Replacing /GR with /GR- instead of applying both options to the project.  This should reduce some build bot warnings (D9025: "overriding '/GR' with '/GR-'").

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187836 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/cmake/modules/AddLLVM.cmake b/cmake/modules/AddLLVM.cmake
index f0b31ce..094969c 100644
--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -191,7 +191,7 @@
   if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
     set(target_compile_flags "${target_compile_flags} -fno-rtti")
   elseif (MSVC)
-    set(target_compile_flags "${target_compile_flags} /GR-")
+    llvm_replace_compiler_option(target_compile_flags "/GR" "/GR-")
   endif ()
 
   if (SUPPORTS_NO_VARIADIC_MACROS_FLAG)