clang-cl: Warn when a /TC or /TP argument is unused

Test Plan: The patch includes a test case.

Reviewers: hansw

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D5338

llvm-svn: 217710
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index e448eb1..c4d983f 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -987,8 +987,8 @@
   Arg *InputTypeArg = nullptr;
 
   // The last /TC or /TP option sets the input type to C or C++ globally.
-  if (Arg *TCTP = Args.getLastArg(options::OPT__SLASH_TC,
-                                  options::OPT__SLASH_TP)) {
+  if (Arg *TCTP = Args.getLastArgNoClaim(options::OPT__SLASH_TC,
+                                         options::OPT__SLASH_TP)) {
     InputTypeArg = TCTP;
     InputType = TCTP->getOption().matches(options::OPT__SLASH_TC)
         ? types::TY_C : types::TY_CXX;