libjson-c: fix host-build

Add -Wno-implicit-fallthrough to HOST_CFLAGS.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
(cherry picked from commit 5e9470a)

package/libs/libjson-c/Makefile

@@ -30,6 +30,7 @@ include $(INCLUDE_DIR)/package.mk
 include $(INCLUDE_DIR)/host-build.mk
 
 TARGET_CFLAGS += $(FPIC) -Wno-implicit-fallthrough
+HOST_CFLAGS += -Wno-implicit-fallthrough
 
 define Package/libjson-c
   SECTION:=libs