Sign Built Packages

[mfeit-internet2]

Add support for signing built packages. GPG appears common to both.

RPM:

• https://access.redhat.com/articles/3359321
• https://hussainaliakbar.github.io/signing-and-verifying-rpm-packages/

Debian:

• https://www.debian.org/doc/manuals/securing-debian-manual/deb-pack-sign.en.html
• https://hussainaliakbar.github.io/digitally-signing-and-verification-of-debian-packages-with-dpkg-sig/

[mfeit-internet2]

Andy says no need for this.