Tests: Update RunCMake.CheckCompilerFlag for Xcode 15.3

Xcode passes a new `-use-frontend-parseable-output` flag to Swift that
conflicts with our `-parseable-output` flag.  Use a different flag for
the test case.

Tests/RunCMake/CheckCompilerFlag/CheckCompilerFlagSwift.cmake

@@ -12,9 +12,9 @@ if(SHOULD_FAIL)
   message(SEND_ERROR "invalid Swift compile flag didn't fail.")
 endif()
 
-check_compiler_flag(Swift "-parseable-output" SHOULD_WORK)
+check_compiler_flag(Swift "-Onone" SHOULD_WORK)
 if(NOT SHOULD_WORK)
-  message(SEND_ERROR "Swift compiler flag '-parseable-output' check failed")
+  message(SEND_ERROR "Swift compiler flag '-Onone' check failed")
 endif()
 
 # Reset locale