Reference MicroBuild.Core unconditionally

The conditional reference caused this package to not apply to the .NET Core build, meaning that the NuGet package was only partially signed, not including the netcoreapp2.0 one.

Fixes #71.

Co-authored-by: Ben Villalobos <bevillal@microsoft.com>

src/MSBuildLocator/Microsoft.Build.Locator.csproj

@@ -23,10 +23,10 @@
   <ItemGroup Condition="'$(TargetFramework)'=='net46'">
     <PackageReference Include="Microsoft.VisualStudio.Setup.Configuration.Interop" Version="1.16.30" PrivateAssets="all" />
     <PackageReference Include="Microsoft.VisualStudio.SDK.EmbedInteropTypes" Version="15.0.21" PrivateAssets="all" />
-    <PackageReference Include="MicroBuild.Core" Version="0.3.0" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>
+    <PackageReference Include="MicroBuild.Core" Version="0.3.0" PrivateAssets="all" />
     <Content Include="build\Microsoft.Build.Locator.props">
       <CopyToOutputDirectory>Never</CopyToOutputDirectory>
       <PackagePath>build\</PackagePath>