x11-servers/xwayland-devel: update to 21.0.99.1.644

Changes: https://gitlab.freedesktop.org/xorg/xserver/-/compare/777c3e000...cad42fcb0
(cherry picked from commit 18d9409b936086a2b3dc7f98232ece2de4f005ff)
(cherry picked from commit ad9e7348d0521f743a758c0f4bf95150d4a4ecbc)