Ignore exit code returned from the merged wrappers (#64651)

JanV noticed that crash in one of the merged wrappers automatically
fails the test execution script so that subsequent wrappers and
the legacy xUnit wrappers don't get run. This simple change fixes
the issue by ignoring the wrapper exit code.

Thanks

Tomas

src/tests/Common/tests.targets

@@ -79,9 +79,12 @@
   </Target>
 
   <Target Name="RunSingleMergedTest">
-    <Exec Command="chmod +x $(TestWrapperScript)" WorkingDirectory="$(BaseOutputPathWithConfig)" Condition="'$(TargetOS)' != 'windows'" />
-    <Exec Command="$(TestWrapperScript) &gt;$(RedirectOutputToFile)" WorkingDirectory="$(BaseOutputPathWithConfig)" Timeout="$(__TestTimeout)" />
-    <Copy SourceFiles="$(TestResultsXmlFile)" DestinationFiles="$(TestResultsCopyTo)" />
+    <Exec Command="chmod +x $(TestWrapperScript)" WorkingDirectory="$(BaseOutputPathWithConfig)" EchoOff="true" Condition="'$(TargetOS)' != 'windows'" />
+    <Exec Command="$(TestWrapperScript) &gt;$(RedirectOutputToFile)" WorkingDirectory="$(BaseOutputPathWithConfig)" Timeout="$(__TestTimeout)" IgnoreExitCode="true">
+      <Output TaskParameter="ExitCode" PropertyName="MergedTestExitCode" />
+    </Exec>
+    <Copy SourceFiles="$(TestResultsXmlFile)" DestinationFiles="$(TestResultsCopyTo)" Condition="'$(MergedTestExitCode)' == '0'" />
+    <Message Importance="High" Text="Error running test group '$(TestWrapperScript)' - exit code $(MergedTestExitCode)" Condition="'$(MergedTestExitCode)' != '0'" />
   </Target>
 
   <Target Name="RunMergedTests" DependsOnTargets="PrepareTestsToRun">