Move portable RID graph into runtime and clean-up

1. Move portable RID graph into runtime
2. Allow updates to both the non-portable and portable RID graphs under
   source build.
3. Clean-up project and remove hacks

Author: ViktorHofer

Directory.Build.props

@@ -471,4 +471,11 @@
     <CustomBeforeNoTargets>$(RepositoryEngineeringDir)NoTargetsSdk.BeforeTargets.targets</CustomBeforeNoTargets>
     <CustomAfterTraversalTargets>$(RepositoryEngineeringDir)TraversalSdk.AfterTargets.targets</CustomAfterTraversalTargets>
   </PropertyGroup>
+
+  <PropertyGroup>
+    <!-- Keep in sync with outputs defined in Microsoft.NETCore.Platforms.csproj. -->
+    <BundledRuntimeIdentifierGraphFile>$([MSBuild]::NormalizePath('$(ArtifactsBinDir)', 'Microsoft.NETCore.Platforms', 'runtime.json'))</BundledRuntimeIdentifierGraphFile>
+    <BundledRuntimeIdentifierGraphFile Condition="!Exists('$(BundledRuntimeIdentifierGraphFile)')">$([MSBuild]::NormalizePath('$(LibrariesProjectRoot)', 'Microsoft.NETCore.Platforms', 'src', 'runtime.json'))</BundledRuntimeIdentifierGraphFile>
+  </PropertyGroup>
+
 </Project>

Directory.Build.targets

@@ -216,4 +216,5 @@
       <InstallersRelativePath>Runtime/$(SharedFrameworkNugetVersion)/</InstallersRelativePath>
     </PropertyGroup>
   </Target>
+
 </Project>

eng/AvoidRestoreCycleOnSelfReference.targets

@@ -128,7 +128,6 @@
   <Import Project="$(RepositoryEngineeringDir)slngen.targets" Condition="'$(IsSlnGen)' == 'true'" />
 
   <Import Project="$(RepositoryEngineeringDir)illink.targets" Condition="'$(IsSourceProject)' == 'true' or '$(ExplicitlyImportCustomILLinkTargets)' == 'true'" />
-  <Import Project="$(RepositoryEngineeringDir)AvoidRestoreCycleOnSelfReference.targets" Condition="'$(AvoidRestoreCycleOnSelfReference)' == 'true'" />
   <Import Project="$(RepositoryEngineeringDir)nativeSanitizers.targets" />
 
   <ItemGroup Condition="'$(UseTargetFrameworkPackage)' != 'false'">

src/libraries/Directory.Build.targets

@@ -0,0 +1,9 @@
+<Project>
+
+  <PropertyGroup>
+    <IsSourceProject>false</IsSourceProject>
+  </PropertyGroup>
+
+  <Import Project="..\..\Directory.Build.props" />
+
+</Project>