--- afboot-stm32-f7f109f0c6f65534ae50f9243a7356c5002a9b87.orig/Makefile	2016-04-24 20:35:00.000000000 +0200
+++ afboot-stm32-f7f109f0c6f65534ae50f9243a7356c5002a9b87/Makefile	2016-04-24 20:36:36.000000000 +0200
@@ -1,14 +1,15 @@
 CROSS_COMPILE ?= arm-none-eabi-
 
-CC = $(CROSS_COMPILE)gcc
-LD = $(CROSS_COMPILE)ld
-OBJCOPY = $(CROSS_COMPILE)objcopy
-OBJDUMP = $(CROSS_COMPILE)objdump
+CC ?= $(CROSS_COMPILE)gcc
+LD ?= $(CROSS_COMPILE)ld
+OBJCOPY ?= $(CROSS_COMPILE)objcopy
+OBJDUMP ?= $(CROSS_COMPILE)objdump
 SIZE = $(CROSS_COMPILE)size
 GDB = $(CROSS_COMPILE)gdb
 OPENOCD = openocd
 
-CFLAGS := -mthumb -mcpu=cortex-m4
+CFLAGS ?= 
+CFLAGS += -mthumb -mcpu=cortex-m4
 CFLAGS += -ffunction-sections -fdata-sections
 CFLAGS += -Os -std=gnu99 -Wall
 LINKERFLAGS := -nostartfiles --gc-sections