[PATCH v4 1/2] mk: fix cross build errors

[Gavin Hu <gavin.hu@arm.com>]

The "-Wimplicit-fallthrough=2" option was introduced into gcc 7.0, it was
enabled when the cross compiler gcc is greater than 7.0, but for the host
side buildtools/pmdinfogen, if the native is older than 7.0, it should not
be enabled.

The fix is to simply enable -Wnoimplicit-fallthrough for pmdinfogen.

gcc -Wp,-MD,./.pmdinfogen.o.d.tmp  -W -Wall -Wstrict-prototypes
-Wmissing-prototypes -Wmissing-declarations -Wold-style-definition
-Wpointer-arith -Wcast-align -Wnested-externs -Wcast-qual
-Wformat-nonliteral -Wformat-security -Wundef -Wwrite-strings -Wdeprecated
-Werror -Wimplicit-fallthrough=2 -Dbbb -Wno-format-truncation -g
-I/home/gavin/arm_repo/dpdk/build/include    -o pmdinfogen.o -c
~/dpdk/buildtools/pmdinfogen/pmdinfogen.c gcc: error:
unrecognized command line option ‘-Wimplicit-fallthrough=2’
~/dpdk/mk/internal/rte.compile-pre.mk:114: recipe for target 'pmdinfogen.o'
failed make[3]: *** [pmdinfogen.o] Error 1

Fixes: ced3e6f8 ("mk: adjust gcc flags for new gcc 7 warnings")
Cc: stable@dpdk.org

Signed-off-by: Gavin Hu <gavin.hu@arm.com>
Reviewed-by: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>
Reviewed-by: Steve Capper <Steve.Capper@arm.com>
Reviewed-by: Thomas Monjalon <thomas@monjalon.net>
Reviewed-by: Bruce Richardson <bruce.richardson@intel.com>
---
 buildtools/pmdinfogen/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/buildtools/pmdinfogen/Makefile b/buildtools/pmdinfogen/Makefile
index bf07b6f..8ee6427 100644
--- a/buildtools/pmdinfogen/Makefile
+++ b/buildtools/pmdinfogen/Makefile
@@ -41,7 +41,7 @@ HOSTAPP = dpdk-pmdinfogen
 #
 SRCS-y += pmdinfogen.c
 
-HOST_CFLAGS += $(WERROR_FLAGS) -g
+HOST_CFLAGS += -Wno-implicit-fallthrough $(WERROR_FLAGS) -g
 HOST_CFLAGS += -I$(RTE_OUTPUT)/include
 
 include $(RTE_SDK)/mk/rte.hostapp.mk
-- 
2.1.4