Recommended way to start numlockx before gdm?

[John Mahowald]

I maintain numlockx in extras. I have recieved requests for it to be
started before gdm, so the keypad works with the numbers while logging
in. [1] Currently it drops a one-liner script into
/etc/X11/xinit/xinitrc.d/numlockx.sh. Is there a way to do it that
earlier in the X startup that isn't too hacky? I'm not an expert on
the X start process by any means. Appending a line to
/etc/X11/xdm/Xsetup_0 has been suggested, is this acceptable?

[1] https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=171361