The `./pyca-cryptography/.travis/downstream.d` subdirectory that causes the `rm` command to fail (albeit harmlessly, but with a warning from `make` nonetheless).
Exclude directories from being matched by the `find` commands.
CLA: trivial
Reviewed-by: Patrick Steuer <patrick.steuer@de.ibm.com> Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10264)