Switch docker base image to alpine, and remove container after compil…

…ation (#5)

* Switch docker base image to alpine, and remove container after compilation.
* Remove unnecessary ADD command in Dockerfile

Dockerfile

@@ -1,10 +1,12 @@
-FROM ubuntu
+FROM alpine
 
 MAINTAINER Kelvin Abrokwa ([email protected])
 
 # install dependencies
-RUN apt-get update && apt-get install -y \
-        build-essential \
+RUN apk add --update \
+        alpine-sdk \
         gcc-avr \
         binutils-avr \
         avr-libc
+
+WORKDIR firmware/

Makefile

@@ -31,7 +31,7 @@ $(HEX): $(BINARY)
 
 docker-build:
 	docker build -t firmware-builder .
-	docker run -it -v `pwd`/:/firmware firmware-builder /bin/bash -c "cd firmware; make"
+	docker run --rm -v `pwd`/:/firmware firmware-builder make
 
 flash-arduino-uno: $(HEX)
 	avrdude -c $(PROGRAMMER) -p $(MMCU) -P $(USB) -U flash:w:$< -v