* Add an alternative method for keyboard discovery to speed up build
* Chain MAKEFLAGS for docker_build.sh
* Slight improvement to number of items sent to sort
* Remove debug line
* Fix line escape
* Add a Docker build script
* Add usage and error messages
* Add -r to reads
Thanks mechmerlin
* Add keyboard:keymap form, improve script
* Add target argument, change usage forms in script
* Add check for more than 3 args in keyboard:keymap:target form
* Change Docker base image to debian, use community repo
This matches what qmk_compiler uses (https://github.com/qmk/qmk_compiler/blob/master/Dockerfile#L1).
I've removed the maintainer as we now have a community build on Docker Hub (https://hub.docker.com/r/qmkfm/qmk_firmware). This Dockerfile will also be maintained by the community.
* Change build command format to keyboard:keymap
* Call make directly in container run command
* Simplify script, remove 3-arg form
* Add COPY to Dockerfile so images are usable in and of themselves
Also change WORKDIR from /qmk to /qmk_firmware
* Add USB pass-through for Linux and docker-machine hosts
* Read directly into variables instead of array
* Alphabetically sort dependencies in Dockerfile
* Set executable bit on util/docker_build.sh
* Update Docker docs
* Add warning about Docker on Windows
* Expand comment in docs
* Check docker-machine exit code instead of string
* Only match --help with whole arguments
* Make script POSIX-compliant
* Convert script indentation to tabs
