Revert "Using an invalid -O falls back on -O3 instead of an error"

This reverts commit r194403.

Was breaking too many tests...



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@194420 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 87ec763..c69ad53 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2727,7 +2727,7 @@
   // preprocessed inputs and configure concludes that -fPIC is not supported.
   Args.ClaimAllArgs(options::OPT_D);
 
-  // Manually translate -O4 to -O3; let clang fall back on -O3 for others
+  // Manually translate -O4 to -O3; let clang reject others.
   if (Arg *A = Args.getLastArg(options::OPT_O_Group)) {
     if (A->getOption().matches(options::OPT_O4)) {
       CmdArgs.push_back("-O3");