correct gcc version major comparison

examples/build_system/make/toolchain/arm_gcc.mk

diff --git a/examples/build_system/make/toolchain/arm_gcc.mk b/examples/build_system/make/toolchain/arm_gcc.mk
index 071b13f..b87657f 100644
--- a/examples/build_system/make/toolchain/arm_gcc.mk
+++ b/examples/build_system/make/toolchain/arm_gcc.mk
@@ -10,6 +10,7 @@
 SIZE = $(CROSS_COMPILE)size
 
 CC_VERSION := $(shell $(CC) -dumpversion)
+CC_VERSION_MAJOR = $(firstword $(subst ., ,$(CC_VERSION)))
 
 # ---------------------------------------
 # Compiler Flags
@@ -73,6 +74,6 @@
 endif
 
 # from version 12
-ifeq (12,$(firstword $(sort 12 $(CC_VERSION))))
+ifeq ($(shell expr $(CC_VERSION_MAJOR) \>= 12),1)
 LDFLAGS += -Wl,--no-warn-rwx-segment
 endif

hw/bsp/stm32f1/family.mk

diff --git a/hw/bsp/stm32f1/family.mk b/hw/bsp/stm32f1/family.mk
index c9321c3..d3627f4 100644
--- a/hw/bsp/stm32f1/family.mk
+++ b/hw/bsp/stm32f1/family.mk
@@ -40,6 +40,5 @@
 SRC_S_GCC += $(ST_CMSIS)/Source/Templates/gcc/startup_$(MCU_VARIANT).s
 SRC_S_IAR += $(ST_CMSIS)/Source/Templates/iar/startup_$(MCU_VARIANT).s
 
-# flash target ROM bootloader
-flash-dfu-util: $(BUILD)/$(PROJECT).bin
-	dfu-util -R -a 0 --dfuse-address 0x08000000 -D $<
+# flash target ROM bootloader: flash-dfu-util
+DFU_UTIL_OPTION = -a 0 --dfuse-address 0x08000000