ubsan: remove redundant -Wno-maybe-uninitialized

Patch series "Clean up UBSAN Makefile", v2.

This series attempts to address the issues seen with UBSAN's object-size
sanitizer causing problems under GCC.  In the process, the Kconfig and
Makefile are refactored to do all the cc-option calls in the Kconfig.
Additionally start to detangle -Wno-maybe-uninitialized, disable
UBSAN_TRAP under COMPILE_TEST for wider build coverage, and expand the
libusan tests.

This patch (of 7):

In commit 78a5255ffb ("Stop the ad-hoc games with
-Wno-maybe-initialized") -Wmaybe-uninitialized was disabled globally, so
keeping the disabling logic here too doesn't make sense.

Link: https://lkml.kernel.org/r/20201203004437.389959-1-keescook@chromium.org
Link: https://lkml.kernel.org/r/20201203004437.389959-2-keescook@chromium.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Nathan Chancellor <natechancellor@gmail.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Marco Elver <elver@google.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: George Popescu <georgepope@android.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Peter Oberparleiter <oberpar@linux.ibm.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/Kconfig.ubsan

@@ -72,10 +72,6 @@ config UBSAN_MISC
 config UBSAN_SANITIZE_ALL
 	bool "Enable instrumentation for the entire kernel"
 	depends on ARCH_HAS_UBSAN_SANITIZE_ALL
-
-	# We build with -Wno-maybe-uninitilzed, but we still want to
-	# use -Wmaybe-uninitilized in allmodconfig builds.
-	# So dependsy bellow used to disable this option in allmodconfig
 	depends on !COMPILE_TEST
 	default y
 	help

scripts/Makefile.ubsan

@@ -31,7 +31,3 @@ endif
 ifdef CONFIG_UBSAN_TRAP
       CFLAGS_UBSAN += $(call cc-option, -fsanitize-undefined-trap-on-error)
 endif
-
-      # -fsanitize=* options makes GCC less smart than usual and
-      # increase number of 'maybe-uninitialized false-positives
-      CFLAGS_UBSAN += $(call cc-option, -Wno-maybe-uninitialized)