In commit 2c0eaf5c4f support was added for
install scripts to accept found programs, built executables, or custom targets.
In commit c239ce31f5, this was extended to
dist and postconf scripts too (although it was documented that those
should not accept targets that are built by ninja).
Despite the commit/PR claiming that all of these should always accept
files and configured files, this was only true for arguments other than
the first, until commit f808c955ea.
In amongst all this, FeatureNew checks were never registered for the
first argument, only for additional arguments, until late in the game
with the addition of FeatureNew checks for File objects.
Fix this in part by moving the 3 different File checks into one, inside the
function that processes the first script, and make that function check
for FeatureNew on anything else too.
f6eaf55906