Use -std instead of --std

--std isn't standardised. lol.

Signed-off-by: Callum Farmer <gmbr3@opensuse.org>

Make.defaults

@@ -125,9 +125,9 @@ ifeq ($(ARCH),x86_64)
                                  && [ $(GCCMINOR) -ge "7" ] ) ) \
                           && echo 1)
   ifeq ($(GCCNEWENOUGH),1)
-    CPPFLAGS += -DGNU_EFI_USE_MS_ABI -maccumulate-outgoing-args --std=c11
+    CPPFLAGS += -DGNU_EFI_USE_MS_ABI -maccumulate-outgoing-args -std=c11
   else ifeq ($(USING_CLANG),clang)
-    CPPFLAGS += -DGNU_EFI_USE_MS_ABI --std=c11
+    CPPFLAGS += -DGNU_EFI_USE_MS_ABI -std=c11
   endif
 
   CFLAGS += -mno-red-zone