Created Building st-flash (markdown)

Building-st-flash.md

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+This page gives a quick overview of how to build and install stlink (which includes st-flash).
+
+These instructions were done under Ubuntu 14.04 LTS.
+
+###Install Pre-requisites###
+You'll need some build tools. It's possible that there are some prerequisites missing here.
+```
+sudo apt-get install libusb-dev
+sudo apt-get install autoconf
+sudo apt-get install build-essential
+```
+
+###Build stlink###
+```
+git clone https://github.com/texane/stlink
+cd stlink
+./autogen.sh
+./configure
+make
+sudo make install
+```
+
+###Install udev rules###
+```
+sudo cp 49*.rules /etc/udev/rules.d
+udevadm control --reload-rules
+udevadm trigger
+```
+
+###Flashing MicroPython using st-flash###
+I normally create a GNUmakefile (in the stmhal directory) which looks something like the following:
+```
+$(info Executing GNUmakefile)
+
+BOARD = STM32F7DISC
+$(info BOARD = $(BOARD))
+
+include Makefile
+
+.PHONY: stlink
+stlink: $(BUILD)/firmware.elf
+	$(ECHO) "Writing flash"
+	$(Q)$(OBJCOPY) -O binary -j .isr_vector $^ $(BUILD)/firmware0.bin
+	$(Q)st-flash write $(BUILD)/firmware0.bin 0x08000000
+	$(Q)$(OBJCOPY) -O binary -j .text -j .data $^ $(BUILD)/firmware1.bin
+	$(Q)st-flash --reset write $(BUILD)/firmware1.bin 0x08020000
+```
+and then you can use ```make stlink``` to flash the micropython image using st-flash