As now we build only when necessary, we need to make sure the images are
built similarly. The discrepancies between the two are less now, and
they can share the same logic.
This fixes a regresion where when no prelude is defined, the build
context isn't copied over
Fixes races conditions and make the DB Switchable. Also prepare inside
the CompilationSpec the tree of the deps to be built, and parallelize
only the building jobs.
Closes#7
Signed-off-by: Ettore Di Giacinto <mudler@gentoo.org>
