Some drivers rely on strpbrk and complain about a lack of strchr().
This is caused by gcc's builtin strpbrk which must be disabled.
CFLAGS := $(CPPFLAGS) -Wall -Wstrict-prototypes -Wno-trigraphs -O2 \
-fno-strict-aliasing -fno-common
-CFLAGS += -fno-builtin-sprintf
+CFLAGS += -fno-builtin-sprintf -fno-builtin-strpbrk
ifndef CONFIG_FRAME_POINTER
CFLAGS += -fomit-frame-pointer
endif