Docker recipe to build a customised exim4-daemon-wormnet .deb,
inspired by http://patchlog.com/linux/debian-building-custom-exim-packages/
Invoke with docker build -t exim-build .; for me on my laptop
it takes about two minutes to prepare the build environment, and
about three minutes to compile Exim.
You can then docker run -it exim-build and work out where to put the .deb files
I'm not proud of this--it contains much thuggery; any contributions to make it less brutal (but still work) most welcome.