This is a regression from c05e615. doom.el changes user-emacs-directory
to doom-cache-dir, which may not exist yet, at the time of this check,
causing file-attributes to return nil, and causing = to throw a type
error (see #6754).
In addition to fixing this, I've also made the check more liberal about
failures, in the odd case that doom-emacs-dir, too, does not exist at
the time bin/doom is called (it'd be very hard to pull that off, but not
impossible).
Fix: #6754
Amend: c05e61536e
ceae154751