extrawarn: enable format and stringop overflow warnings in W=1

The stringop and format warnings got disabled globally when they were
newly introduced in commit bd664f6b ("disable new gcc-7.1.1 warnings
for now"), 217c3e01 ("disable stringop truncation warnings for now")
and 5a76021c ("gcc-10: disable 'stringop-overflow' warning for now").

In all cases, the sentiment at the time was that the warnings are
useful, and we actually addressed a number of real bugs based on
them, but we never managed to eliminate them all because even the
build bots using W=1 builds only see the -Wstringop-truncation
warnings that are enabled at that level.

Move these into the W=1 section to give them a larger build coverage
and actually eliminate them over time.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.extrawarn

@@ -16,8 +16,6 @@ KBUILD_CFLAGS += -Werror=strict-prototypes
 KBUILD_CFLAGS += -Wno-format-security
 KBUILD_CFLAGS += -Wno-trigraphs
 KBUILD_CFLAGS += $(call cc-disable-warning,frame-address,)
-KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
-KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
 KBUILD_CFLAGS += $(call cc-disable-warning, address-of-packed-member)
 
 ifneq ($(CONFIG_FRAME_WARN),0)
@@ -56,9 +54,6 @@ KBUILD_CFLAGS += -Wno-pointer-sign
 # globally built with -Wcast-function-type.
 KBUILD_CFLAGS += $(call cc-option, -Wcast-function-type)
 
-# We'll want to enable this eventually, but it's not going away for 5.7 at least
-KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
-
 # Another good warning that we'll want to enable eventually
 KBUILD_CFLAGS += $(call cc-disable-warning, restrict)
 
@@ -111,6 +106,9 @@ KBUILD_CFLAGS += -Wmissing-include-dirs
 KBUILD_CFLAGS += $(call cc-option, -Wunused-but-set-variable)
 KBUILD_CFLAGS += $(call cc-option, -Wunused-const-variable)
 KBUILD_CFLAGS += $(call cc-option, -Wpacked-not-aligned)
+KBUILD_CFLAGS += $(call cc-option, -Wformat-overflow)
+KBUILD_CFLAGS += $(call cc-option, -Wformat-truncation)
+KBUILD_CFLAGS += $(call cc-option, -Wstringop-overflow)
 KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation)
 
 KBUILD_CPPFLAGS += -Wundef
@@ -123,6 +121,9 @@ else
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-but-set-variable)
 KBUILD_CFLAGS += $(call cc-disable-warning, unused-const-variable)
 KBUILD_CFLAGS += $(call cc-disable-warning, packed-not-aligned)
+KBUILD_CFLAGS += $(call cc-disable-warning, format-overflow)
+KBUILD_CFLAGS += $(call cc-disable-warning, format-truncation)
+KBUILD_CFLAGS += $(call cc-disable-warning, stringop-overflow)
 KBUILD_CFLAGS += $(call cc-disable-warning, stringop-truncation)
 
 ifdef CONFIG_CC_IS_CLANG