gnome.desktop is not being install to $DESTDIR/usr/share/wayland-sessions when $DESTDIR is defined.

meson.build can't do it, as meson does not yet support copying the same file to multiple targets

# FIXME: The same target can not be copied into two directories.
#        There is a workaround in meson_post_install.py until proper solution arises:
#        https://groups.google.com/forum/#!topic/mesonbuild/3iIoYPrN4P0


and meson_post_install.py does not do it when DESTDIR is defined:

if not os.environ.get('DESTDIR'):
[…]
  # FIXME: this is due to unable to copy a generated target file:
  #        https://groups.google.com/forum/#!topic/mesonbuild/3iIoYPrN4P0
  dst_dir = os.path.join(sys.argv[1], 'wayland-sessions')
  if not os.path.exists(dst_dir):
    os.makedirs(dst_dir)