Driver: Ignore -fobjc-gc and -fobjc-gc-only for platforms which don't support them.

llvm-svn: 100930
diff --git a/clang/lib/Driver/ToolChains.cpp b/clang/lib/Driver/ToolChains.cpp
index 4bb3246..80dea50 100644
--- a/clang/lib/Driver/ToolChains.cpp
+++ b/clang/lib/Driver/ToolChains.cpp
@@ -663,6 +663,11 @@
   return 0;
 }
 
+bool Darwin::SupportsObjCGC() const {
+  // Garbage collection is supported everywhere except on iPhone OS.
+  return !isTargetIPhoneOS();
+}
+
 /// Generic_GCC - A tool chain using the 'gcc' command to perform
 /// all subcommands; this relies on gcc translating the majority of
 /// command line options.