`--force-accept-unsigned` requires GPG to be installed

[theseer]

--force-accept-unsigned still fails if GPG is not installed.

$ phive --no-progress install --force-accept-unsigned <my-repo>
Phive 0.16.0 - Copyright (C) 2015-2025 by Arne Blankerts, Sebastian Heuer and Contributors
[ERROR]    No executable gpg binary found.  
[ERROR]     Either install gpg or enable the gnupg extension in PHP.

Originally posted by @XedinUnknown in #134