gpgme-config and gpg-error-config not found

[jeremie-dautheribes]

Hello,

On Ubuntu 24.04 LTS, gpgme-config and gpg-error-config, which were provided on previous versions by libgpgme-dev and libgpg-error-dev respectively, are no longer shipped.
These tools are needed when building dev dependencies. I had to compile and install both tools manually to get it to work.

I don't know if you would like to warn the user in the "Hacking" section. I can make a patch if you want.