Add Golang environment and support for cross-compiling.

Add docker entrypoint script for compiling Mender client
and running mender-convert.

Changelog: Support compiling Mender client in mender-convert container.

Signed-off-by: Eystein Måløy Stenberg <eystein.maloy.stenberg@northern.tech>

docker/Dockerfile

@@ -2,6 +2,7 @@ FROM ubuntu:18.04
 
 ARG MENDER_ARTIFACT_VERSION=2.3.0
 ARG MENDER_CONVERT_VERSION=1.0.0
+ARG GOLANG_VERSION=1.11.2
 
 RUN apt-get update && apt-get install -y \
     kpartx \
@@ -46,7 +47,15 @@ RUN wget -nc -q http://releases.linaro.org/components/toolchain/binaries/6.3-201
 RUN wget -q -O /usr/bin/mender-artifact https://d1b0l86ne08fsf.cloudfront.net/mender-artifact/$MENDER_ARTIFACT_VERSION/mender-artifact \
     && chmod +x /usr/bin/mender-artifact
 
+# Golang environment, for cross-compiling the Mender client
+RUN wget https://dl.google.com/go/go$GOLANG_VERSION.linux-amd64.tar.gz \
+    && tar -C /usr/local -xzf go$GOLANG_VERSION.linux-amd64.tar.gz \
+    && echo export PATH=$PATH:/usr/local/go/bin >> /root/.bashrc
 
 # TODO: support selecting tag of mender-convert with MENDER_CONVERT_VERSION
 # TODO: consider lighter way to download to avoid git dependency
 RUN git clone https://github.com/mendersoftware/mender-convert.git
+
+
+COPY docker-entrypoint.sh /usr/local/bin/
+ENTRYPOINT ["/usr/local/bin/docker-entrypoint.sh"]

docker/docker-entrypoint.sh

@@ -0,0 +1,33 @@
+#!/bin/sh
+
+set -e
+
+MENDER_CLIENT_VERSION="1.7.0b1"  # TODO: Take as argument or env variable
+
+
+echo "Cross-compiling Mender client $MENDER_CLIENT_VERSION"
+# NOTE: we are assuming generic ARM board here, needs to be extended later
+
+export PATH=$PATH:/usr/local/go/bin
+export GOPATH=$HOME/go
+export PATH=$PATH:/gcc-linaro-6.3.1-2017.05-x86_64_arm-linux-gnueabihf/bin
+
+go get github.com/mendersoftware/mender
+cd $GOPATH/src/github.com/mendersoftware/mender
+git checkout $MENDER_CLIENT_VERSION
+
+env CGO_ENABLED=1 \
+    CC=arm-linux-gnueabihf-gcc \
+    GOOS=linux \
+    GOARCH=arm make build
+
+cp $GOPATH/src/github.com/mendersoftware/mender/mender /
+
+
+# run conversion, args provided to container (end of docker run ...)
+
+cd /mender-convert
+
+echo "Running mender-convert "$@""
+
+./mender-convert "$@"