test/Driver/lit.local.cfg

config.suffixes = ['.c', '.cpp', '.h', '.m', '.mm', '.S', '.s', '.f90', '.f95',
                   '.cu']
config.substitutions = list(config.substitutions)
config.substitutions.insert(0,
    ('%clang_cc1',
     """*** Do not use 'clang -cc1' in Driver tests. ***""") )