the current Xsession check sets xsession to "You should reconfigure
--with-xsession" which cause confusing problems if not caught when
attempting to log in: /bin/sh: You: command not found
I think the AC_MSG_WARN should be changed into AC_MSG_ERROR .. or the
default of /etc/X11/xdm/Xsession be used..
I recently set up an build box, and this bit me, as I had xorg-x11-libs
but not xorg-x11 installed .. configure didn't find Xsession, and hence
the above scenario played out .. I spent quite a few minutes desperately
trying to figure it out.. once I looked at the messages log, I saw the
full message, and spent the next minutes twiddling with configure on the
build box until I found out that I needed to have xorg-x11 installed.