diff --git a/BuildToolsVersion.txt b/BuildToolsVersion.txt
index db085adb34c7..ba407aecdd77 100644
--- a/BuildToolsVersion.txt
+++ b/BuildToolsVersion.txt
@@ -1 +1 @@
-1.0.27-prerelease-01230-01
\ No newline at end of file
+1.0.27-prerelease-01302-01
diff --git a/Tools-Override/Build.Common.props b/Tools-Override/Build.Common.props
index b19202316b59..d5d48a116240 100644
--- a/Tools-Override/Build.Common.props
+++ b/Tools-Override/Build.Common.props
@@ -23,10 +23,12 @@
 
   <!-- Platform detection -->
   <PropertyGroup>
-    <OsEnvironment Condition="'$(OsEnvironment)'=='' AND '$(OS)'=='Unix' AND Exists('/Applications')">OSX</OsEnvironment>
-    <OsEnvironment Condition="'$(OsEnvironment)'=='' AND '$(OS)'=='Unix'">Linux</OsEnvironment>
-    <OsEnvironment Condition="'$(OsEnvironment)'==''">$(OS)</OsEnvironment>
-    <RunningOnUnix Condition="'$(OS)' != 'Windows_NT'">true</RunningOnUnix>
+    <DefaultOSGroup Condition="'$(OS)'=='Unix' AND Exists('/Applications')">OSX</DefaultOSGroup>
+    <DefaultOSGroup Condition="'$(DefaultOSGroup)'=='' AND '$(OS)'=='Unix'">Linux</DefaultOSGroup>
+    <DefaultOSGroup Condition="'$(DefaultOSGroup)'==''">$(OS)</DefaultOSGroup>
+    <RunningOnUnix Condition="'$(OS)'!='Windows_NT'">true</RunningOnUnix>
+
+    <RunningOnCore Condition="'$(MSBuildRuntimeType)' == 'core'">true</RunningOnCore>
   </PropertyGroup>
 
   <!-- Common BuildTools properties -->
@@ -35,9 +37,10 @@
     <ToolRuntimePath Condition="'$(ToolRuntimePath)'=='' and '$(ProjectDir)'!=''">$(ProjectDir)Tools/</ToolRuntimePath>
     <ToolsDir Condition="'$(ToolsDir)'==''">$(MSBuildThisFileDirectory)</ToolsDir>
     <DotnetCliPath Condition="'$(DotnetCliPath)'==''">$(ToolRuntimePath)dotnetcli/</DotnetCliPath>
-    <OverrideToolHost>$(DotnetCliPath)dotnet</OverrideToolHost>
-    <BuildToolsTaskDir Condition="'$(MSBuildRuntimeType)'!='core'">$(ToolsDir)net45/</BuildToolsTaskDir>
-    <BuildToolsTaskDir Condition="'$(MSBuildRuntimeType)'=='core'">$(ToolsDir)</BuildToolsTaskDir>
+    <OverrideToolHost Condition="'$(RunningOnUnix)' == 'true'">$(DotnetCliPath)dotnet</OverrideToolHost>
+    <OverrideToolHost Condition="'$(RunningOnUnix)' != 'true'">$(DotnetCliPath)dotnet.exe</OverrideToolHost>
+    <BuildToolsTaskDir Condition="'$(RunningOnCore)'!='true'">$(ToolsDir)net45/</BuildToolsTaskDir>
+    <BuildToolsTaskDir Condition="'$(RunningOnCore)'=='true'">$(ToolsDir)</BuildToolsTaskDir>
     <UseRoslynCompilers Condition="'$(UseRoslynCompilers)'=='' and '$(RunningOnUnix)'=='true'">false</UseRoslynCompilers>
     <UseSharedCompilation Condition="'$(UseSharedCompilation)' == '' and '$(RunningOnUnix)' != 'true' and '$(UseRoslynCompilers)' != 'false'">true</UseSharedCompilation>
   </PropertyGroup>
diff --git a/Tools-Override/CodeCoverage.targets b/Tools-Override/CodeCoverage.targets
index e815791d3939..3b1e952ac5d3 100644
--- a/Tools-Override/CodeCoverage.targets
+++ b/Tools-Override/CodeCoverage.targets
@@ -13,7 +13,7 @@
   <!-- Coverage options -->
   <PropertyGroup>
     <CodeCoverageEnabled>false</CodeCoverageEnabled>
-    <CodeCoverageEnabled Condition="'$(SkipTests)' != 'true' and '$(OS)' == 'Windows_NT' and '$(Coverage)' == 'true' and '$(Performance)' != 'true'">true</CodeCoverageEnabled>
+    <CodeCoverageEnabled Condition="'$(SkipTests)' != 'true' and '$(RunningOnUnix)' != 'true' and '$(Coverage)' == 'true' and '$(Performance)' != 'true'">true</CodeCoverageEnabled>
     <CoverageReportDir Condition="'$(CoverageReportDir)' == ''">$(TestWorkingDir)coverage\</CoverageReportDir>
 
     <!-- This targets file has two modes one for individual projects and one for all -->
diff --git a/Tools-Override/ConstructSharedFx.targets b/Tools-Override/ConstructSharedFx.targets
index b2793c83559e..38c931f57475 100644
--- a/Tools-Override/ConstructSharedFx.targets
+++ b/Tools-Override/ConstructSharedFx.targets
@@ -22,19 +22,17 @@
           
     <ItemGroup>
       <!-- This will only copy over the related file -->
-      <HostFxrFile Condition="'$(OS)'=='Windows_NT'" Include="$(RuntimePath)hostfxr.dll" />
-      <HostFxrFile Condition="'$(OS)'=='Unix'" Include="$(RuntimePath)libhostfxr.so" />
-      <HostFxrFile Condition="'$(OS)'=='Unix'" Include="$(RuntimePath)libhostfxr.dylib" />
-      <DotnetExe Condition="'$(OS)'=='Windows_NT'" Include="$(RuntimePath)dotnet.exe" />
-      <DotnetExe Condition="'$(OS)'!='Windows_NT'" Include="$(RuntimePath)dotnet" />
+      <HostFxrFile Condition="'$(OSGroup)'=='Windows_NT'" Include="$(RuntimePath)hostfxr.dll" />
+      <HostFxrFile Condition="'$(OSGroup)'=='Linux'" Include="$(RuntimePath)libhostfxr.so" />
+      <HostFxrFile Condition="'$(OSGroup)'=='OSX'" Include="$(RuntimePath)libhostfxr.dylib" />
+      <DotnetExe Condition="'$(RunningOnUnix)'!='true'" Include="$(RuntimePath)dotnet.exe" />
+      <DotnetExe Condition="'$(RunningOnUnix)'=='true'" Include="$(RuntimePath)dotnet" />
     </ItemGroup>
     <MakeDir Directories="$(TestSharedFxPathHostFxr)" />
     <Copy SourceFiles="@(HostFxrFile)" 
-          DestinationFolder="$(TestSharedFxPathHostFxr)" 
-          Condition="Exists('%(RootDir)%(Directory)%(Filename)%(Extension)')" />
+          DestinationFolder="$(TestSharedFxPathHostFxr)" />
     <Copy SourceFiles="@(DotnetExe)" 
-          DestinationFolder="$(TestSharedFxDir)" 
-          Condition="Exists('%(RootDir)%(Directory)%(Filename)%(Extension)')" />
+          DestinationFolder="$(TestSharedFxDir)" />
     <ItemGroup>
       <LiveDotNetCliComponents Include="$(RuntimePath)\*.*" Exclude="$(RuntimePath)\xunit.console.netcore.exe" />
     </ItemGroup>
diff --git a/Tools-Override/Roslyn.Common.props b/Tools-Override/Roslyn.Common.props
index 95baca28736f..cdeed2881031 100755
--- a/Tools-Override/Roslyn.Common.props
+++ b/Tools-Override/Roslyn.Common.props
@@ -3,16 +3,17 @@
   <PropertyGroup>
     <RoslynVersion>2.0.0-beta3</RoslynVersion>
     <RoslynPackageName>Microsoft.Net.Compilers</RoslynPackageName>
+    <RoslynTargetsPath>$(ToolRuntimePath)</RoslynTargetsPath>
   </PropertyGroup>
 
   <PropertyGroup>
-    <RoslynPropsFile Condition="'$(RoslynPropsFile)' == '' and '$(RunningOnUnix)' != 'true'">$(ToolRuntimePath)/net45/roslyn/build/Microsoft.Net.Compilers.props</RoslynPropsFile>
+    <RoslynPropsFile Condition="'$(RoslynPropsFile)' == '' and '$(RunningOnCore)' != 'true'">$(ToolRuntimePath)/net45/roslyn/build/Microsoft.Net.Compilers.props</RoslynPropsFile>
   </PropertyGroup>
 
   <!--
     On Unix we always use a version of Roslyn we restore from NuGet and we have to work around some known issues.
   -->
-  <PropertyGroup Condition="'$(RoslynPropsFile)' == '' and '$(RunningOnUnix)' == 'true'">
+  <PropertyGroup Condition="'$(RoslynPropsFile)' == '' and '$(RunningOnCore)' == 'true'">
     <RoslynPackageDir>$(PackagesDir)/$(RoslynPackageName).$(RoslynVersion)/</RoslynPackageDir>
     <RoslynPropsFile>$(RoslynPackageDir)build/$(RoslynPackageName).props</RoslynPropsFile>
 
diff --git a/Tools-Override/codeAnalysis.targets b/Tools-Override/codeAnalysis.targets
index fd8a8161ca2c..99093978239b 100644
--- a/Tools-Override/codeAnalysis.targets
+++ b/Tools-Override/codeAnalysis.targets
@@ -5,8 +5,8 @@
     always be net45 (because we use Mono to run our tests and Mono needs to load the net45 version)
   -->
   <PropertyGroup>
-    <CodeAnalyzerDir Condition="'$(CodeAnalyzerDir)'=='' and '$(OSEnvironment)'=='Windows_NT'">$(ToolsDir)net45/analyzers/</CodeAnalyzerDir>
-    <CodeAnalyzerDir Condition="'$(CodeAnalyzerDir)'=='' and '$(OSEnvironment)'!='Windows_NT'">$(ToolsDir)analyzers/</CodeAnalyzerDir>
+    <CodeAnalyzerDir Condition="'$(CodeAnalyzerDir)'=='' and '$(RunningOnCore)'!='true'">$(ToolsDir)net45/analyzers/</CodeAnalyzerDir>
+    <CodeAnalyzerDir Condition="'$(CodeAnalyzerDir)'=='' and '$(RunningOnCore)'=='true'">$(ToolsDir)analyzers/</CodeAnalyzerDir>
   </PropertyGroup>
 
   <!-- PInvokeChecker data files-->
diff --git a/Tools-Override/tests.targets b/Tools-Override/tests.targets
index c1ec7c7fc880..068a31a252d6 100644
--- a/Tools-Override/tests.targets
+++ b/Tools-Override/tests.targets
@@ -246,10 +246,8 @@
   </Target>
 
   <Target Name="CheckTestPlatforms">
-    <GetTargetMachineInfo Condition="'$(TargetOS)' == ''">
-      <Output TaskParameter="TargetOS" PropertyName="TargetOS" />
-    </GetTargetMachineInfo>
     <PropertyGroup>
+      <TargetOS Condition="'$(TargetOS)' == ''">$(DefaultOSGroup)</TargetOS>
       <TestDisabled Condition="'%(UnsupportedPlatformsItems.Identity)' == '$(TargetOS)' Or '$(ConfigurationErrorMsg)' != ''">true</TestDisabled>
     </PropertyGroup>
     <Message Text="CheckTestPlatforms found TargetOS of [$(TargetOS)]." Importance="Low" />
diff --git a/Tools-Override/versioning.targets b/Tools-Override/versioning.targets
index f550f9ccb698..23799bc22ab6 100644
--- a/Tools-Override/versioning.targets
+++ b/Tools-Override/versioning.targets
@@ -263,10 +263,10 @@
     </ItemGroup>
     <!-- Windows Exec command requires DOS escaping for the percent sign since it secretly runs the process in a shell instead of calling createprocess. -->
     <PropertyGroup>
-      <LatestDateCommand Condition="'$(OsEnvironment)'=='Windows_NT'">git show -s --format=^%25%25cd --date=short HEAD</LatestDateCommand>
-      <LatestDateCommand Condition="'$(OsEnvironment)'!='Windows_NT'">git show -s --format=%25cd --date=short HEAD</LatestDateCommand>
+      <LatestDateCommand Condition="'$(RunningOnUnix)'!='true'">git show -s --format=^%25%25cd --date=short HEAD</LatestDateCommand>
+      <LatestDateCommand Condition="'$(RunningOnUnix)'=='true'">git show -s --format=%25cd --date=short HEAD</LatestDateCommand>
     </PropertyGroup>
-      
+
     <Exec Command="$(LatestDateCommand)" StandardOutputImportance="Low" IgnoreExitCode="true" IgnoreStandardErrorWarningFormat="true" ConsoleToMSBuild="true">
       <Output TaskParameter="ConsoleOutput" PropertyName="VersionSeedDate" />
       <Output TaskParameter="ExitCode" PropertyName="LatestDateCommandExitCode" />
diff --git a/dir.props b/dir.props
index f07560c075c7..4dc8daf3266a 100644
--- a/dir.props
+++ b/dir.props
@@ -150,7 +150,7 @@
       See Documentation/coding-guidelines/project-guidelines.md for more details on our configurations.
     -->
     <TargetGroup Condition="'$(TargetGroup)' == ''">netcoreapp</TargetGroup>
-    <OSGroup Condition="'$(OSGroup)' == ''">$(OSEnvironment)</OSGroup>
+    <OSGroup Condition="'$(OSGroup)' == ''">$(DefaultOSGroup)</OSGroup>
     <ConfigurationGroup Condition="'$(ConfigurationGroup)' == ''">Debug</ConfigurationGroup>
     <ArchGroup Condition="'$(ArchGroup)' == ''">x64</ArchGroup>