Skip xunit trimming descriptors for wasm build tests

Fails because it can't find `xunit.runner.utility.netcoreapp10`

Author: radical

eng/testing/tests.mobile.targets

@@ -243,7 +243,7 @@
     </ItemGroup>
 
     <ItemGroup>
-      <TrimmerRootDescriptor Include="$(MSBuildThisFileDirectory)ILLink.Descriptor.xunit.xml" />
+      <TrimmerRootDescriptor Include="$(MSBuildThisFileDirectory)ILLink.Descriptor.xunit.xml" Condition="'$(SkipXunitTrimmerDescriptor)' != 'true'"  />
       <TrimmerRootDescriptor Include="$(MSBuildThisFileDirectory)ILLink.Descriptor.TestUtilities.xml" Condition="'$(SkipTestUtilitiesReference)' != 'true'" />
     </ItemGroup>
   </Target>

src/tests/BuildWasmApps/Wasm.Build.Tests/Wasm.Build.Tests.csproj

@@ -2,6 +2,7 @@
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppToolCurrent)</TargetFrameworks>
     <SkipTestUtilitiesReference>true</SkipTestUtilitiesReference>
+    <SkipXunitTrimmerDescriptor>true</SkipXunitTrimmerDescriptor>
     <IsTestProject>true</IsTestProject>
     <BundleXunitRunner>true</BundleXunitRunner>
     <CLRTestKind>BuildAndRun</CLRTestKind>