Don't use IBC on .NET Core (#41593)

This changes our build so that we don't apply IBC optimization data to
our .NET Core binaries. This data is only applicable for .NET Desktop
scenarios.

Author: jaredpar

src/Compilers/CSharp/Portable/Microsoft.CodeAnalysis.CSharp.csproj

@@ -8,7 +8,7 @@
     <TargetFrameworks>netcoreapp3.1;netstandard2.0</TargetFrameworks>
     <CodeAnalysisRuleSet>..\CSharpCodeAnalysisRules.ruleset</CodeAnalysisRuleSet>
     <GenerateMicrosoftCodeAnalysisCommitHashAttribute>true</GenerateMicrosoftCodeAnalysisCommitHashAttribute>
-    <ApplyNgenOptimization>partial</ApplyNgenOptimization>
+    <ApplyNgenOptimization Condition="'$(TargetFramework)' == 'netstandard2.0'">partial</ApplyNgenOptimization>
 
     <!-- NuGet -->
     <IsPackable>true</IsPackable>

src/Compilers/Core/Portable/Microsoft.CodeAnalysis.csproj

@@ -9,7 +9,7 @@
     <DefineConstants>$(DefineConstants);COMPILERCORE</DefineConstants>
     <CodeAnalysisRuleSet>..\CodeAnalysisRules.ruleset</CodeAnalysisRuleSet>
     <NoStdLib>true</NoStdLib>
-    <ApplyNgenOptimization>partial</ApplyNgenOptimization>
+    <ApplyNgenOptimization Condition="'$(TargetFramework)' == 'netstandard2.0'">partial</ApplyNgenOptimization>
     <GeneratePerformanceSensitiveAttribute>true</GeneratePerformanceSensitiveAttribute>
 
     <!-- NuGet -->