build: Genericize the toolchain config.

Makefile.common

@@ -3,7 +3,11 @@ TOP:=$(shell readlink -f "$(dir $(lastword $(MAKEFILE_LIST)))")
 
 -include $(TOP)/Makefile.opts
 
-# Toolchain
+# Toolchain - Don't change this unless you are sure what you're doing!
+TOOLCHAIN_CONFIG=toolchain-$(MCU_CORE).config
+TOOLCHAIN_SRC_DIR=crosstool-ng
+CROSS_DIR=${HOME}/x-tools/arm-$(MCU_CORE)-eabi
+CROSS_COMPILE=${CROSS_DIR}/bin/arm-$(MCU_CORE)-eabi-
 CC=$(CROSS_COMPILE)gcc
 CPP=$(CROSS_COMPILE)cpp
 LD=$(CROSS_COMPILE)gcc

libs/stm32f10x.mk

@@ -1,10 +1,5 @@
-# Toolchain configuration.  Don't change unless you know what you're doing!
-TOOLCHAIN_CONFIG=toolchain-cm3.config
-TOOLCHAIN_SRC_DIR=crosstool-ng
-#-1.19.0
-CROSS_DIR=${HOME}/x-tools/arm-cm3-eabi
-CROSS_COMPILE=${CROSS_DIR}/bin/arm-cm3-eabi-
-
+# The processor!
+MCU_CORE=cm3
 # Set up include paths
 MCU_INCLUDE += -I$(LIBDIR)/CMSIS/Include
 MCU_INCLUDE += -I$(LIBDIR)/CMSIS/Device/ST/STM32F10x/Include