GCC compatibility: Create a Group to ignore unsupported optimization.

Returns a warning when using an unknown optimization flag.
This patch includes -finline-limit as one of those ignored flags.
More options will be moved in this group

Patch by Arthur Marble <arthur@info9.net> in the context of
Debian Google Summer of code 2014.

Reviewers: rnk, Sylvestre
llvm-svn: 212805
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index cac20a1..3846d47 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -3138,6 +3138,13 @@
     }
   }
 
+  // Warn about ignored options to clang.
+  for (arg_iterator it = Args.filtered_begin(
+       options::OPT_clang_ignored_gcc_optimization_f_Group),
+       ie = Args.filtered_end(); it != ie; ++it) {
+    D.Diag(diag::warn_ignored_gcc_optimization) << (*it)->getAsString(Args);
+  }
+
   // Don't warn about unused -flto.  This can happen when we're preprocessing or
   // precompiling.
   Args.ClaimAllArgs(options::OPT_flto);