Revert r66765 and r66766. These were causing build failures on Darwin.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@66770 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Makefile.rules b/Makefile.rules
index 59d8440..66d90f1 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -522,11 +522,13 @@
   # Building universal cannot compute dependencies automatically.
   DISABLE_AUTO_DEPENDENCIES=1
 else
-  ifeq ($(ARCH),x86_64)
-    CompileCommonOpts += -m64
-  else
-    ifeq ($(ARCH),x86)
-      CompileCommonOpts += -m32
+  ifeq ($(OS),Darwin)
+    ifeq ($(ARCH),x86_64)
+      CompileCommonOpts += -m64
+    else
+      ifeq ($(ARCH),x86)
+        CompileCommonOpts += -m32
+      endif
     endif
   endif
 endif