ci: Use common build script for libwayland

Rather than open-coding libwayland install for each container, create a
common build script like the rest, using both git and meson like the
rest.

Signed-off-by: Daniel Stone <daniels@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11248>

.gitlab-ci/container/build-wayland.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -ex
+
+export LIBWAYLAND_VERSION="1.18.0"
+
+git clone https://gitlab.freedesktop.org/wayland/wayland
+cd wayland
+git checkout "$LIBWAYLAND_VERSION"
+meson -Ddocumentation=false -Ddtd_validation=false -Dlibraries=true _build
+ninja -C _build install
+cd ..
+rm -rf wayland