[DNM] Silence some C++ interop test failures

Author: AnthonyLatsis

test/Interop/lit.local.cfg

@@ -6,7 +6,7 @@ def get_target_os():
     (run_cpu, run_vendor, run_os, run_version) = re.match('([^-]+)-([^-]+)-([^0-9]+)(.*)', config.variant_triple).groups()
     return run_os
 
-clang_compile_opt = '-I' + config.swiftlib_dir + ' '
+clang_compile_opt = '-I' + config.swiftlib_dir + ' -Wno-unreachable-code-return -Wno-unreachable-code '
 clang_opt = clang_compile_opt
 
 is_cf_options_interop_updated = True