[Tools] Pass --delete_unversioned_trees to gclient sync.

Change fetch_deps.py so that we remove repositories that are no longer used;
especially when we move to different Chromium versions and the repositories
we track change.
    [Tizen] Pure wayland build fix

    Pure wayland build need to avoid the BuildRequire for all X11 libraries.

    Signed-off-by: Yannick GICQUEL <yannick.gicquel@open.eurogiciel.org>