Merge pull request bitcraze#47 from rallen10/master

adding test for docker arg

docker/gap8/Dockerfile

@@ -4,6 +4,7 @@ FROM ubuntu:18.04
 ENV DEBIAN_FRONTEND noninteractive 
 ARG GAP_SDK_VERSION
 RUN echo $GAP_SDK_VERSION
+RUN test -n "$GAP_SDK_VERSION"
 
 # Install needed packages
 RUN apt-get update && apt-get install -y build-essential git libftdi-dev libftdi1 doxygen python3-pip libsdl2-dev curl cmake libusb-1.0-0-dev scons gtkwave libsndfile1-dev rsync autoconf automake texinfo libtool pkg-config libsdl2-ttf-dev 
@@ -37,7 +38,7 @@ RUN pip3 install h5py==2.10.0
 RUN /bin/bash -c "cd gap_sdk/; source configs/ai_deck.sh; ls; make nntool"
 
 
-RUN apt-get install -y libopencv-dev python3-opencv
+RUN apt-get update && apt-get install -y libopencv-dev python3-opencv
 
 RUN /bin/bash -c "cd gap_sdk/; source configs/ai_deck.sh; ls; make gap_tools"
 

docs/getting-started/docker-gap8.md

@@ -20,7 +20,7 @@ echo 'export GAP_SDK_VERSION=3.8.1' >> ~/.bashrc
 _Note: if you would like to also build docker images for SDK version 3.4, 3.5, 3.6 or 3.7, just replace the previous version number. The build process will checkout the right version of the SDK_
 
 ```
-docker build --tag gapsdk:${GAP_SDK_VERSION} --build-arg GAP_SDK_VERSION .
+docker build --tag gapsdk:${GAP_SDK_VERSION} --build-arg GAP_SDK_VERSION=$GAP_SDK_VERSION .
 ```
 
 Open up the container to install the auto tiler