Tests: Teach RunCMake to ignore Xcode internal objc warnings

Xcode on Apple Silicon warns:

    objc[...]: Class AMSupportURL... is implemented in both ...
    One of the two will be used. Which one is undefined.

Teach RunCMake to drop such lines before matching against expected
output.

Tests/RunCMake/RunCMake.cmake

@@ -153,6 +153,7 @@ function(run_cmake test)
     "|contact PGI Sales at"
 
     "|[^\n]*xcodebuild[^\n]*warning: file type[^\n]*is based on missing file type"
+    "|[^\n]*objc[^\n]*: Class AMSupportURL[^\n]* One of the two will be used. Which one is undefined."
     "|[^\n]*is a member of multiple groups"
     "|[^\n]*offset in archive not a multiple of 8"
     "|[^\n]*from Time Machine by path"