clang-cl: use -fno-rtti by default

Generating RTTI in the MS ABI is currently not supported, and the failures
are confusing to users, so let's disable it by default for now.

llvm-svn: 202178
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 690c07f..7167fcc 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -4112,6 +4112,10 @@
   if (Arg *A = Args.getLastArg(options::OPT_show_includes))
     A->render(Args, CmdArgs);
 
+  // RTTI is currently not supported, so disable it by default.
+  if (!Args.hasArg(options::OPT_frtti, options::OPT_fno_rtti))
+    CmdArgs.push_back("-fno-rtti");
+
   const Driver &D = getToolChain().getDriver();
   Arg *MostGeneralArg = Args.getLastArg(options::OPT__SLASH_vmg);
   Arg *BestCaseArg = Args.getLastArg(options::OPT__SLASH_vmb);