ubsan: fix tree-wide -Wmaybe-uninitialized false positives

-fsanitize=* options makes GCC less smart than usual and increase number
of 'maybe-uninitialized' false-positives. So this patch does two things:

 * Add -Wno-maybe-uninitialized to CFLAGS_UBSAN which will disable all
   such warnings for instrumented files.

 * Remove CONFIG_UBSAN_SANITIZE_ALL from all[yes|mod]config builds. So
   the all[yes|mod]config build goes without -fsanitize=* and still with
   -Wmaybe-uninitialized.

Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index e07c1ba..39494af 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -13,6 +13,11 @@
 	bool "Enable instrumentation for the entire kernel"
 	depends on UBSAN
 	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
 	  This option activates instrumentation for the entire kernel.