livebuild: Prevent users from configuring archives in lb config

Since the OBS live-build only has access to the configured repositories
(due to the lack of network access) the user shall not configure archives
inside the configuration itself.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
livebuild: create local repository in $BUILD_ROOT/.build.binaries

Instead of creating the repository in $TOPDIR/SOURCES/repos this is
adapting to what mock is doing.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
livebuild: Write system default configuration to /etc/live/build.conf

This reduces the amount of code required in the livebuild_pre_run hook.

Signed-off-by: Jan Blunck <jblunck@infradead.org>
livebuild: Run OBS buildroot livebuild_pre_run hook before user provided one

We should not change the buildroot between the lb config and the lb build
calls. Therefore move the OBS buildroot hook to run first.

Signed-off-by: Jan Blunck <jblunck@infradead.org>