bug#25360: File mode specification errors during building

[Glenn Morris]

Thanks.
I can't decide whether modifying loadup.el for bootstrap-emacs in all
cases is good, bad, or neither... :)
Does it have any impact on the speed of builds, either way?
(Eg no longer loading something that wasn't needed;
or now autoloading every time something that used to be dumped.)

BTW, did you consider using a non-Emacs method to generate the basic loaddefs?
Eg maybe find + awk would be good enough to extract the necessary
autoloads to get a bootstrap going?