Makefile: Update clang warning disables from Linux

Re-sync the logic about which clang warnings to disable from v4.17-rc1.
Note that we don't disable all of the same ones as for now we haven't
run into any cases of warnings from clang in code from upstream Linux.

Signed-off-by: Tom Rini <trini@konsulko.com>

Makefile

@@ -610,6 +610,13 @@ endif
 endif
 
 KBUILD_CFLAGS += $(call cc-option,-Wno-format-nonliteral)
+ifeq ($(cc-name),clang)
+KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
+KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
+KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
+KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
+KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior)
+endif
 
 # turn jbsr into jsr for m68k
 ifeq ($(ARCH),m68k)