buildman: Add a --boards option to specify particular boards to build

At present 'buildman sandbox' will build all 5 boards for the sandbox
architecture rather than the single board 'sandbox'. The only current way
to exclude sandbox_spl, sandbox_noblk, etc. is to use -x which is a bit
clumbsy.

Add a --boards option to allow individual build targets to be specified.

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