Use in-tree ilasm to run test suite natively on s390x (#71326)

* There are no linux-s390x packages on nuget.org, so use in-tree
  built ilasm when running the test suite natively on s390x

Author: uweigand

Directory.Build.props

@@ -115,7 +115,7 @@
     <MonoAOTCompilerTasksAssemblyPath>$([MSBuild]::NormalizePath('$(MonoAOTCompilerDir)', 'MonoAOTCompiler.dll'))</MonoAOTCompilerTasksAssemblyPath>
     <MonoTargetsTasksAssemblyPath>$([MSBuild]::NormalizePath('$(MonoTargetsTasksDir)', 'MonoTargetsTasks.dll'))</MonoTargetsTasksAssemblyPath>
     <TestExclusionListTasksAssemblyPath>$([MSBuild]::NormalizePath('$(TestExclusionListTasksDir)', 'TestExclusionListTasks.dll'))</TestExclusionListTasksAssemblyPath>
-    <ILAsmToolPath Condition="'$(DotNetBuildFromSource)' == 'true'">$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'coreclr', '$(TargetOS).$(TargetArchitecture).$(Configuration)'))</ILAsmToolPath>
+    <ILAsmToolPath Condition="'$(DotNetBuildFromSource)' == 'true' or '$(BuildArchitecture)' == 's390x'">$([MSBuild]::NormalizeDirectory('$(ArtifactsBinDir)', 'coreclr', '$(TargetOS).$(TargetArchitecture).$(Configuration)'))</ILAsmToolPath>
   </PropertyGroup>
 
   <PropertyGroup Label="CalculateConfiguration">