buildman - U-Boot multi-threaded builder and summary tool

This tool handles building U-Boot to check that you have not broken it
with your patch series. It can build each individual commit and report
which boards fail on which commits, and which errors come up. It also
shows differences in image sizes due to particular commits.

Buildman aims to make full use of multi-processor machines.

Documentation and caveats are in tools/buildman/README.

Signed-off-by: Simon Glass <sjg@chromium.org>