Add tests on how clang currently handles some unknown options.

This is not to say this is the desired behavior, but it makes sure we notice
if it changes.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@191242 91177308-0d34-0410-b5e6-96231b3b80d8

test/Driver/unknown-arg.c

@@ -4,3 +4,10 @@
 // CHECK: unknown argument
 // CHECK: unknown argument
 // CHECK: unknown argument
+
+
+// RUN: %clang -S %s -o %t.s -funknown-to-clang-option -Wunknown-to-clang-option -munknown-to-clang-optio
+
+// IGNORED: warning: argument unused during compilation: '-funknown-to-clang-option'
+// IGNORED: warning: argument unused during compilation: '-munknown-to-clang-option'
+// IGNORED: warning: unknown warning option '-Wunknown-to-clang-option'