Allow source-build cache setup if SetUpSourceBuildIntermediateNupkgCache is true (#15854)

Author: ellahathaway

src/Microsoft.DotNet.Arcade.Sdk/tools/SourceBuild/SourceBuildArcadeTools.targets

@@ -11,10 +11,6 @@
     <PackageReference Include="Microsoft.DotNet.SourceBuild.Tasks" Version="$(MicrosoftDotNetSourceBuildTasksVersion)" IsImplicitlyDefined="true" />
   </ItemGroup>
 
-  <PropertyGroup>
-    <SetUpSourceBuildIntermediateNupkgCache Condition="'$(SetUpSourceBuildIntermediateNupkgCache)' == ''">true</SetUpSourceBuildIntermediateNupkgCache>
-  </PropertyGroup>
-
   <!-- Because the condition here is rather complex, it should read as the following:
       - Don't collect intermediates if running the product build
       - Otherwise, collect if we're forcing it using SetUpSourceBuildIntermediateNupkgCache

src/Microsoft.DotNet.Arcade.Sdk/tools/Tools.proj

@@ -92,8 +92,13 @@
         Condition="'$(Restore)' == 'true'"/>
   </Target>
 
+  <PropertyGroup>
+    <SetUpSourceBuildIntermediateNupkgCache Condition="'$(SetUpSourceBuildIntermediateNupkgCache)' == ''">true</SetUpSourceBuildIntermediateNupkgCache>
+  </PropertyGroup>
+
   <Import Project="SourceBuild/SourceBuildArcadeTools.targets" Condition="'$(ArcadeBuildFromSource)' == 'true' or
-                                                                          '$(DotNetBuildRepo)' == 'true'" />
+                                                                          '$(DotNetBuildRepo)' == 'true' or
+                                                                          '$(SetUpSourceBuildIntermediateNupkgCache)' == 'true'" />
 
   <!-- Repository extensibility point -->
   <Import Project="$(RepositoryEngineeringDir)Tools.props" Condition="Exists('$(RepositoryEngineeringDir)Tools.props')" />