Merge: Improve initial make

Small improvement to make the initial make better.
For the final user perspective, an useless error message is removed and the whole process should be slightly faster.

Before:

* real time with cleared ccache: 4m46s
* user time with cleared ccache: 13m23s
* real time with full ccache: 42.5s
* user time with full ccache: 41.8s

After:

* real time with cleared ccache: 4m30s (-5.6%)
* user time with cleared ccache: 13m23s (-4.6%)
* real time with full ccache: 42.5s (-27.8%)
* user time with full ccache: 41.8s (-24.63)

Pull-Request: #1585
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>