Tests: Teach RunCMake to ignore Xcode DVTCoreDeviceEnabledState warnings

On some Xcode versions, xcodebuild may warn:

... xcodebuild[...] DVTCoreDeviceEnabledState: DVTCoreDeviceEnabledState_Disabled set via user default

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

Backport: release