... and fix the REQUIRES_RTTI condition.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@81524 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Makefile.rules b/Makefile.rules
index 5f442d3..8d1e621 100644
--- a/Makefile.rules
+++ b/Makefile.rules
@@ -343,8 +343,8 @@
   LD.Flags  := $(filter-out -fomit-frame-pointer,$(LD.Flags))
 endif
 
-# IF REQUIRES_RTTI=1 is specified then don't disable run-time type id
-ifndef REQUIRES_RTTI
+# If REQUIRES_RTTI=1 is specified then don't disable run-time type id.
+ifeq ($(REQUIRES_RTTI), 1)
   CXX.Flags := $(filter-out -fno-rtti,$(CXX.Flags))
   CXXFLAGS := $(filter-out -fno-rtti,$(CXXFLAGS))
 endif