Makefile: Enable -Wzero-length-bounds

With all known internal zero-length accesses fixed, it is possible to
enable -Wzero-length-bounds globally. Since this is included by default
in -Warray-bounds, we just need to stop disabling it.

Cc: "Gustavo A. R. Silva" <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Masahiro Yamada <[email protected]>
Cc: [email protected]
Signed-off-by: Kees Cook <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Link: https://lore.kernel.org/lkml/CAKwvOd=bcs5W6eEDXGn5ROR2EuMiSp_2e6sLFxak=KK6yLWcvA@mail.gmail.com

Author: kees

Makefile

@@ -951,7 +951,6 @@ KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
 
 # We'll want to enable this eventually, but it's not going away for 5.7 at least
-KBUILD_CFLAGS += $(call cc-disable-warning, zero-length-bounds)
 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
 
 # Another good warning that we'll want to enable eventually