Disabling CONFIG_BUG creates an insane amount of build warnings, which
makes it useless to check for building defconfigs to see if new
warnings show up.

Without this patch, building tct_hammer_defconfig results in:

net/packet/af_packet.c: In function 'tpacket_rcv':
net/packet/af_packet.c:1889:30: warning: 'hdrlen' may be used uninitialized in this function [-Wuninitialized]
net/core/ethtool.c: In function 'ethtool_get_feature_mask':
net/core/ethtool.c:213:1: warning: control reaches end of non-void function [-Wreturn-type]
block/cfq-iosched.c: In function 'cfq_async_queue_prio':
block/cfq-iosched.c:2914:1: warning: control reaches end of non-void function [-Wreturn-type]
mm/bootmem.c: In function 'mark_bootmem':
mm/bootmem.c:352:1: warning: control reaches end of non-void function [-Wreturn-type]
net/core/dev.c: In function 'skb_warn_bad_offload':
net/core/dev.c:1904:33: warning: unused variable 'null_features' [-Wunused-variable]
drivers/mtd/chips/cfi_probe.c: In function 'cfi_chip_setup':
include/linux/mtd/cfi.h:489:3: warning: 'r.x[0]' may be used uninitialized in this function [-Wuninitialized]
include/linux/mtd/map.h:394:11: note: 'r.x[0]' was declared here
include/linux/mtd/cfi.h:489:3: warning: 'r.x[0]' may be used uninitialized in this function [-Wuninitialized]
(and many more)

The size of vmlinux increases by 1.78% because of this:

size obj-arm/vmlinux.nobug
   text    data     bss     dec     hex filename
   2108474  116916   55352 2280742  22cd26 obj-arm/vmlinux
size obj-arm/vmlinux.bug
   text    data     bss     dec     hex filename
   2150804  116916   53696 2321416  236c08 obj-arm/vmlinux

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>