use simply expanded variables + fix
use simply expanded variables + fix

Use simply expanded variables in Makefile.common for light gain
in performance and also gain more determinism.

Avoid unecessary deb rebuild after rpm build using order-only
prerequisites for the base build directories, that way they don't
trigger rebuild if touched, the only import part is that they exists.

Have a clear "command not found" if cowbuilder is not present instead
of a password prompt (if called with sudo).

kakwa/amkecpak,kakwa/amkecpak