Add GPG encryption support for Arch

[CKMz17]

Hi, thanks for the project. On Arch Linux the packaged build lacks GPG encryption support

[Tech0ne]

+1

Tried my best trying to fix it by cloning the repo locally, and editing PKGBUILD but it's stuck at

checking for gpgme-config... no
checking for GPGME - version >= 0.4.2... no

after adding the --with-gpgme flag to ./configure.