According to @eli-schwartz review
https://github.com/profanity-im/profanity/pull/1619#discussion_r760421795:
```
"notifications" is a feature object. When configured with
-Dnotifications=disabled it logs:
Dependency libnotify skipped: feature notifications disabled
[...]
notifications : disabled
and builds without support.
pgp is a boolean option, which IMHO it shouldn't be. When configured
with -Dpgp=false it logs:
Run-time dependency gpgme found: YES 1.16.0
[...]
pgp : false
which is contradictory and misleading, because it was available
and detected, just not required. So it tries to build with PGP
support.
BUILD_PGP is the Makefile.am define, not the C define. This
should set HAVE_LIBGPGME.
Later, in core_sources_c, check if pgp_dep.found() and add
'src/pgp/gpg.c' as an additional source.
```
