Append EXTRA_CFLAGS to CFLAGS so that additional flags can be applied to
the compiler.

Signed-off-by: Leo Yan <leo.yan@arm.com>
---
 tools/usb/Makefile | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/usb/Makefile b/tools/usb/Makefile
index c6235667dd46223b646bbab5c82c810221750182..42362dcdf2743dace62a5385a7d2707c42bdd3c0 100644
--- a/tools/usb/Makefile
+++ b/tools/usb/Makefile
@@ -14,6 +14,7 @@ endif
 MAKEFLAGS += -r
 
 override CFLAGS += -O2 -Wall -Wextra -g -D_GNU_SOURCE -I$(OUTPUT)include -I$(srctree)/tools/include
+override CFLAGS += $(EXTRA_CFLAGS)
 override LDFLAGS += -lpthread
 
 ALL_TARGETS := testusb ffs-test

-- 
2.34.1