livebuild: Do not substitute while parsing

If the project configuration is changing the source is not parsed again.
Therefore the substitution shall be done in bs_sched and bs_repserver.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
livebuild: Error out if archives are configured

We do not support additional repositories defined in the live-build
configuration so we return an error here.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
Merge pull request #118 from jblunck/livebuild-build-binaries

Move substitution away from parsing code and error out when archives (repos) are configured