Index: llvm/trunk/utils/gn/build/BUILD.gn
===================================================================
--- llvm/trunk/utils/gn/build/BUILD.gn
+++ llvm/trunk/utils/gn/build/BUILD.gn
@@ -28,7 +28,6 @@
     cflags_cc = [
       "-std=c++11",
       "-fno-exceptions",
-      "-fno-rtti",
       "-fvisibility-inlines-hidden",
     ]
   } else {
@@ -52,10 +51,7 @@
       "_UNICODE",
       "UNICODE",
     ]
-    cflags += [
-      "/EHs-c-",
-      "/GR-",
-    ]
+    cflags += [ "/EHs-c-" ]
 
     # The MSVC default value (1 MB) is not enough for parsing recursive C++
     # templates in Clang.
@@ -110,6 +106,14 @@
   }
 }
 
+config("no_rtti") {
+  if (current_os == "win") {
+    cflags_cc = [ "/GR-" ]
+  } else {
+    cflags_cc = [ "-fno-rtti" ]
+  }
+}
+
 config("llvm_code") {
   include_dirs = [
     "//llvm/include",
Index: llvm/trunk/utils/gn/build/BUILDCONFIG.gn
===================================================================
--- llvm/trunk/utils/gn/build/BUILDCONFIG.gn
+++ llvm/trunk/utils/gn/build/BUILDCONFIG.gn
@@ -5,6 +5,7 @@
 shared_binary_target_configs = [
   "//llvm/utils/gn/build:compiler_defaults",
   "//llvm/utils/gn/build:llvm_code",
+  "//llvm/utils/gn/build:no_rtti",
   "//llvm/utils/gn/build:warn_covered_switch_default",
 ]