The C driver will be a direct consumer of this libmongocrypt. The C driver will need to search and link against libmongocrypt if available.

To accomplish this, libmongocrypt needs to create CMake package configuration files on install, similar to what the C driver provides. That way, the C driver can find_package to check if libmongocrypt is installed and possibly link to it.

I don't think it's necessary to create package config files (though I may be wrong).

kms-message already has this: https://github.com/10gen/kms-message
Though I'm hesitant to copy over configuration without fully understanding it.