ci: Setup XDG_RUNTIME_DIR in crosvm-init

This environment variable has to be set to use the wayland platform.

Signed-off-by: Corentin Noël <corentin.noel@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21900>

.gitlab-ci/crosvm-init.sh

@@ -14,6 +14,9 @@ mount -t tmpfs tmpfs /tmp
 
 . ${VM_TEMP_DIR}/crosvm-env.sh
 
+# Required by the wayland platform
+export XDG_RUNTIME_DIR=$(mktemp -d)
+
 # .gitlab-ci.yml script variable is using relative paths to install directory,
 # so change to that dir before running `crosvm-script`
 cd "${CI_PROJECT_DIR}"