aws key management plugin deb packages not being built

The AWS key management plugin is not being built on Debian and Ubuntu. Looks like it started not building after 10.3.5 was released.

In the build log there are `dh_missing` entries that say the following:

dh_missing: usr/lib/mysql/plugin/aws_key_management.so exists in debian/tmp but is not installed to anywhere

dh_missing: etc/mysql/conf.d/aws_key_management.cnf exists in debian/tmp but is not installed to anywhere

http://buildbot.askmonty.org/buildbot/builders/kvm-deb-artful-amd64/builds/1300/steps/compile/logs/stdio

So something is getting built, but the deb package is not getting created for some reason.