rename this test from .S to .c so that it gets run.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@67380 91177308-0d34-0410-b5e6-96231b3b80d8

test/Preprocessor/assembler-with-cpp.c

@@ -1,4 +1,4 @@
-// RUN: clang -E %s &&
+// RUN: clang -x assembler-with-cpp -E %s &&
 // RUN: not clang -x c -E %s
 
 #ifndef __ASSEMBLER__