When --check is ran with no output, this is seen as having *SOME*
invalid outputs, actually, ALL of them are invalid here.
Instead of reporting a confusing error, let's consider ALL of outputs
being invalid to be no output at all available and advise the user to
rerun the build without --check.
If there's *some* (>0) invalid outputs, let's print them exactly to give
a chance to the user to remediate this.
Fixes#485.
Change-Id: I00955ef9ea4f129e2c98d68c73b1e981f90278a0
Signed-off-by: Raito Bezarius <raito@lix.systems>