Add DEBUG flag to Makefile

* Add a DEBUG flag to Makefile, enables: "-O0 -ggdb"

stm/Makefile

@@ -22,8 +22,16 @@ OBJCOPY = arm-none-eabi-objcopy
 SIZE = arm-none-eabi-size
 
 CFLAGS_CORTEX_M4 = -mthumb -mtune=cortex-m4 -mabi=aapcs-linux -mcpu=cortex-m4 -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant -Wdouble-promotion -DSTM32F40XX -DHSE_VALUE=8000000
-CFLAGS = -I. -I$(PY_SRC) -I$(FATFSSRC) -I$(STMSRC) -Wall -ansi -std=gnu99 -Os -DNDEBUG $(CFLAGS_CORTEX_M4) -D$(TARGET)
+CFLAGS = -I. -I$(PY_SRC) -I$(FATFSSRC) -I$(STMSRC) -Wall -ansi -std=gnu99 $(CFLAGS_CORTEX_M4) -D$(TARGET)
 #CFLAGS += -I$(STMOTGSRC) -DUSE_HOST_MODE -DUSE_OTG_MODE
+
+#Debugging/Optimization
+ifeq ($(DEBUG), 1)
+CFLAGS = -O0 -ggdb
+else
+CFLAGS = -Os -DNDEBUG
+endif
+
 LDFLAGS = --nostdlib -T stm32f405.ld
 
 SRC_C = \