[BUILD] Add build system module makefiles, add README how to use it.

mk/gcc-config.mk

@@ -0,0 +1,37 @@
+##
+## This file is part of the libopencm3 project.
+##
+## Copyright (C) 2014 Frantisek Burian <BuFran@seznam.cz>
+##
+## This library is free software: you can redistribute it and/or modify
+## it under the terms of the GNU Lesser General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This library is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU Lesser General Public License for more details.
+##
+## You should have received a copy of the GNU Lesser General Public License
+## along with this library.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+###############################################################################
+# The support makefile for GCC compiler toolchain, the rules part.
+#
+# please read mk/README for specification how to use this file in your project
+
+
+PREFIX		?= arm-none-eabi
+#PREFIX		?= arm-elf
+
+CC		:= $(PREFIX)-gcc
+CXX		:= $(PREFIX)-g++
+LD		:= $(PREFIX)-gcc
+AR		:= $(PREFIX)-ar
+AS		:= $(PREFIX)-as
+OBJCOPY		:= $(PREFIX)-objcopy
+OBJDUMP		:= $(PREFIX)-objdump
+GDB		:= $(PREFIX)-gdb
+SIZE		:= $(PREFIX)-size