ci: re-add EXTRA_LOCAL_PACKAGES to rootfs

This variable was removed on commit
848f59deda when file `create-rootfs.sh`
was splitted.
Re-add it.

This can make it more convenient for other projects to reuse these
scripts.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23894>

.gitlab-ci/container/lava_build.sh

@@ -92,6 +92,7 @@ fi
 apt-get update
 apt-get install -y --no-remove \
 		   -o Dpkg::Options::='--force-confdef' -o Dpkg::Options::='--force-confold' \
+                   ${EXTRA_LOCAL_PACKAGES} \
                    ${ARCH_PACKAGES} \
                    automake \
                    bc \