Driver/Darwin: Honor IPHONEOS_DEPLOYMENT_TARGET.

llvm-svn: 94488
diff --git a/clang/lib/Driver/ToolChains.h b/clang/lib/Driver/ToolChains.h
index 3ca6ad8..89478d5 100644
--- a/clang/lib/Driver/ToolChains.h
+++ b/clang/lib/Driver/ToolChains.h
@@ -54,11 +54,15 @@
   //
   // FIXME: This should go away, such differences should be completely
   // determined by the target triple.
+  //
+  // FIXME: It is also broken, we need to distinguish the "default target" from
+  // the actual target. The -m...-version-min strings and deployment targets can
+  // change this.
   bool IsIPhoneOS;
 
   /// The default macosx-version-min of this tool chain; empty until
   /// initialized.
-  mutable std::string MacosxVersionMin;
+  std::string MacosxVersionMin;
 
   /// The default iphoneos-version-min of this tool chain.
   std::string IPhoneOSVersionMin;