fwknop: gpgme fixes

Relates to #34251, fixing the expectation of finding a ``` gpg ``` executable unless explicitly configured to expect ``` gpg2 ```. Pulled into a new PR to try and isolate the UTF-8 bot errors.
Apologies, I thought 5 options might be pushing it a bit in terms of keeping the formula easily-readable so I yanked the args out into an array. I'll revert.