Disable warning about MSVC not found.

When this test runs on bots that are configured to default
to MSVC, but MSVC isn't actually installed, we can emit a
warning that MSVC is not found.  Since MSVC isn't actually
needed for this test to succeed, just disable this warning.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@297858 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/DiagnosticDriverKinds.td

@@ -286,5 +286,5 @@ def err_drv_defsym_invalid_symval : Error<"Value is not an integer: %0">;
 def warn_drv_msvc_not_found : Warning<
   "unable to find a Visual Studio installation; "
   "try running Clang from a developer command prompt">,
-  InGroup<InvalidOrNonExistentDirectory>;
+  InGroup<DiagGroup<"msvc-not-found">>;
 }

test/Misc/backend-stack-frame-diagnostics.cpp

@@ -8,7 +8,7 @@
 
 // Test that link invocations don't emit an "argument unused during compilation" diagnostic.
 // RUN: touch %t.o
-// RUN: %clang -Werror -Wno-liblto -Wframe-larger-than=0 %t.o -###  2>&1 | not grep ' error: '
+// RUN: %clang -Werror -Wno-msvc-not-found -Wno-liblto -Wframe-larger-than=0 %t.o -###  2>&1 | not grep ' error: '
 
 // TODO: Support rich backend diagnostics for Objective-C methods.