In order to configure different target and build in a different
directory, the build-dir parameter will run configure from a
subdirectory of the root. This allows separating build artifacts
from source code. It allows to build for different targets
at the same time.
Also add support for this in export, run, debug, install, and
uninstall commands.
Do not add it in info command yet.

Apertis: https://phabricator.apertis.org/T3557



Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.com>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.com>
Differential Revision: https://phabricator.apertis.org/D6129