Start running Loader and Interop tests for NativeAOT (#84404)

These are the most interesting ones to cover in regular testing.

Author: MichalStrehovsky

eng/pipelines/runtime.yml

@@ -244,7 +244,7 @@ extends:
             extraStepsTemplate: /eng/pipelines/coreclr/nativeaot-post-build-steps.yml
             extraStepsParameters:
               creator: dotnet-bot
-              testBuildArgs: nativeaot tree nativeaot /p:BuildNativeAotFrameworkObjects=true
+              testBuildArgs: 'nativeaot tree ";nativeaot;Loader;Interop;" /p:BuildNativeAotFrameworkObjects=true'
               liveLibrariesBuildConfig: Release
             testRunNamePrefixSuffix: NativeAOT_$(_BuildConfig)
             extraVariablesTemplates:

src/tests/Directory.Build.targets

@@ -549,6 +549,16 @@
 
     <!-- Bump the generic cycle tolerance. There's at least one test with a cycle that is reachable at runtime to depth 6 -->
     <IlcArg Include="--maxgenericcycle:7" />
+
+    <!-- We set TrimMode to partial so that we don't trim parts of the tests,
+         but don't make this apply to xunit cruft -->
+    <IlcArg Include="--trim:Microsoft.DotNet.XUnitExtensions" />
+    <IlcArg Include="--trim:xunit.abstractions" />
+    <IlcArg Include="--trim:xunit.assert" />
+    <IlcArg Include="--trim:xunit.console" />
+    <IlcArg Include="--trim:xunit.core" />
+    <IlcArg Include="--trim:xunit.execution.dotnet" />
+    <IlcArg Include="--trim:xunit.abstractions" />
   </ItemGroup>
 
   <Import Project="$(CoreCLRBuildIntegrationDir)Microsoft.DotNet.ILCompiler.SingleEntry.targets" Condition="'$(TestBuildMode)' == 'nativeaot'" />