[gdm] (11 commits) ...Merge branch 'meson-fixes' into 'master'

[Ray Strode <halfline src gnome org>]

Summary of changes:

  2c0177a... meson: Fix keyutils pkg-config name
  1cf8c4d... meson: Obey at -Dcustom-conf option when installing custom.
  6629344... meson: Use correct rules path when getting udevdir from pkg
  663612f... README: Update build instructions using meson
  cbd1565... session: Leave to meson the duty of keeping the lists in sy
  aaf82e9... meson: When possible use systemd dirs to check for systemd 
  b01713b... meson: Don't look for non-existent journald dependency
  6d83346... meson_options: Enable systemd-journal by default
  a2d7dc2... meson: Print a summary of configured features (if on meson 
  a798460... meson: Fix Xsession input file name
  62d3617... Merge branch 'meson-fixes' into 'master'