externalsrc: Detect code changes in submodules
Further to
50ff9afb39, only detect code changes in submodules that are
subdirectories of the EXTERNALSRC directory.
git submodule status returns a path relative to the cwd for each submodule.
We don't add submodules that are not within our source subtree.
Signed-off-by: Douglas Royds <douglas.royds@taitradio.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit
4525310d49d115a37705f04ac5c03d639e5e8f8c)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
