[ubsan] Enable testing of .m files

This allows `.m` test files, like the existing Misc/bool.m, to be
tested.

Author: vedantk

compiler-rt/test/ubsan/lit.common.cfg.py

@@ -65,7 +65,7 @@ def build_invocation(compile_flags):
 config.substitutions.append( ("%gmlt ", " ".join(config.debug_info_flags) + " ") )
 
 # Default test suffixes.
-config.suffixes = ['.c', '.cpp']
+config.suffixes = ['.c', '.cpp', '.m']
 
 # Check that the host supports UndefinedBehaviorSanitizer tests
 if config.host_os not in ['Linux', 'Darwin', 'FreeBSD', 'Windows', 'NetBSD', 'SunOS', 'OpenBSD']: