As promised, what I found so far: the following dockerfile yeilds a usable cross-compile environment, provided you use it with a Makefile.
FROM ubuntu:xenial
RUN apt-get update \
&& apt-get install --yes \
vim \
build-essential \
git
RUN git clone https://github.com/raspberrypi/tools
RUN git clone https://gist.github.com/3873805.git /build
WORKDIR "/build"
CMD ["/usr/bin/make", "CC=/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin/arm-linux-gnueabihf-gcc"
, "HelloWorld"]
# Seems I need a real makefile for the above to work.
For cross compiling mysensors to work, hoever, you also need to properly seed the variable in configure, for it to work correctly. This is where I left off.
Sources:
https://stackoverflow.com/questions/18007326/how-to-change-default-values-of-variables-like-cc-in-makefile
https://bitbucket.org/mitchallen/pi-hello-cross-compile/src/master/
https://desertbot.io/blog/how-to-cross-compile-for-raspberry-pi
https://github.com/mitchallen/pi-cross-compile/blob/master/Dockerfile
https://github.com/mysensors/MySensors/blob/development/configure
https://github.com/raspberrypi/tools/tree/master/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin
https://www.raspberrypi.org/documentation/linux/kernel/building.md
https://www.mysensors.org/build/raspberry
