externalsrc: Detect code changes in submodules
Further to
50ff9afb39, only detect code changes in submodules that are
subdirectories of the EXTERNALSRC directory.
The (undocumented) git submodule--helper returns a path
for each submodule relative to the top of the repo.
Don't add submodules that are not within our source subtree.
[YOCTO #14333]
Signed-off-by: Douglas Royds <douglas.royds@taitradio.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit
1c18225d3ef94a41fc073ae87c163b68e6d46571)
Signed-off-by: Steve Sakoman <steve@sakoman.com>
