Feature Request: Custom messages/actions to supplement REQUIRED failures
Having a clean way to supplement REQUIRED error messages of find_program()/find_package()/etc. with something like "As of this writing, glad can be obtained via its homepage <https://github.com/Dav1dde/glad>, or via Debian package 'python3-glad', or via pip3 package 'glad'." would be nice.
As a way of making this less limiting, albeit I don't see much use for it other than making things a bit more convenient, a FAILURE_CALLBACK <function> option can be a possibility.