Move -fcxx-modules to MANDATORY_MODULE_BUILD_CFLAGS (NFC)

git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@354418 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/packages/Python/lldbsuite/test/make/Makefile.rules b/packages/Python/lldbsuite/test/make/Makefile.rules
index a2dc6cc..6d1ca51 100644
--- a/packages/Python/lldbsuite/test/make/Makefile.rules
+++ b/packages/Python/lldbsuite/test/make/Makefile.rules
@@ -284,12 +284,13 @@
 
 MANDATORY_MODULE_BUILD_CFLAGS := -fmodules -gmodules -fmodules-cache-path=$(CLANG_MODULE_CACHE_DIR)
 
+ifeq "$(OS)" "Darwin"
+	MANDATORY_MODULE_BUILD_CFLAGS += -fcxx-modules
+endif
+
 ifeq "$(MAKE_GMODULES)" "YES"
 	CFLAGS += $(MANDATORY_MODULE_BUILD_CFLAGS)
 	CXXFLAGS += $(MANDATORY_MODULE_BUILD_CFLAGS)
-	ifeq "$(OS)" "Darwin"
-		CXXFLAGS += -fcxx-modules
-	endif
 endif
 
 CXXFLAGS += -std=c++11 $(CFLAGS) $(ARCH_CXXFLAGS)