Once the source code is downloaded and the dependencies are
installed, it makes it easier for people to build Replicant.
It also saves the builds logs, to enable to later look at why
the build failed without needing to re-run the build.
However users still have to take care of running repo --sync
if necessary. This ensure that the local modifications are not
lost and also simplifies the procedure for testing patches.
Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>