This reverts commit ca21bbf2ed.

5bf74f2 removed the host build of expat and updated packages to use
tools/expat instead.

ca21bbf re-added the host build of expat for mesa (actually wayland) in
the video feed.

Changing wayland to use tools/expat is the proper fix, and there is a
PR[1] open with this change. Therefore this commit can and should be
reverted.

[1]: https://github.com/openwrt/video/pull/24

Signed-off-by: Jeffery To <jeffery.to@gmail.com>