Mark R2RDumpTests as incompatible with GC stress (#44586)

The purpose of this test is not to stress the runtime, it's relatively
lengthy as it processes the entire System.Private.CoreLib framework
assembly and so it's timing in GC stress runs.

Thanks

Tomas

src/tests/readytorun/r2rdump/FrameworkTests/R2RDumpTests.csproj

@@ -3,6 +3,9 @@
     <OutputType>Exe</OutputType>
     <DisableProjectBuild Condition="'$(RuntimeFlavor)' != 'coreclr'">true</DisableProjectBuild>
     <CLRTestTargetUnsupported Condition="'$(RuntimeFlavor)' != 'coreclr'">true</CLRTestTargetUnsupported>
+    <!-- The test is lengthy as it scans the entire System.Private.CoreLib so that it times out in GC stress runs. -->
+    <!-- The purpose of the test is functional testing of the R2R reader, not runtime stress testing. -->
+    <GCStressIncompatible>true</GCStressIncompatible>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="R2RDumpTester.cs" />