Switch assert(0/false) llvm_unreachable.

llvm-svn: 140367
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index c3c07f4..dba4c22 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2477,7 +2477,7 @@
 const char *darwin::CC1::getCC1Name(types::ID Type) const {
   switch (Type) {
   default:
-    assert(0 && "Unexpected type for Darwin CC1 tool.");
+    llvm_unreachable("Unexpected type for Darwin CC1 tool.");
   case types::TY_Asm:
   case types::TY_C: case types::TY_CHeader:
   case types::TY_PP_C: case types::TY_PP_CHeader: