Overwrite Xsession config

When I copied /usr/share/gdm/Xsession conf to /etc/gdm/Xsession, I see that it not used:

/usr/share/gdm/Xsession: Beginning session setup...
/usr/share/gdm/Xsession: Setup done, will execute: /usr/bin/ssh-agent -- awesome

Xsession called by /usr/libexec/gdm-x-session which have hardcoded location:

ethan@clr-1fc1c0bf41bb45ceb2acf44ba9aa1098~ $ strings /usr/libexec/gdm-x-session | grep Xsession
Run program through /etc/gdm/Xsession wrapper script

I think that first finded value is https://github.com/endlessm/gdm/blob/ef621e086e4ee11822a8c9c0eb39f28cbb6e0638/daemon/gdm-x-session.c#L666
and second is https://github.com/endlessm/gdm/blob/ef621e086e4ee11822a8c9c0eb39f28cbb6e0638/daemon/gdm-x-session.c#L858
Second location for other distrs and not connected with this situation.

How can I make gdm-x-session run with my config from /etc/gdm/Xsession?