Hi Ralf,
I didn't read all related Wiki pages, but seemingly non, including https://wiki.archlinux.org/index.php/makepkg mention Eli's hint, to use
echo 'GNUPGHOME="$HOME"/.gnupg-makepkg' >> "$HOME"/.config/pacman/makepkg.conf
Fortunately the manpage does.
$ man makepkg | grep GNUPGHOME GNUPGHOME="/path/to/directory"
It mentions that environment variable, defined by gpg(1), but makepkg.conf(5) says Configuration options for makepkg are stored in makepkg.conf. This file is sourced so you can include any special compiler flags you wish to use. This is helpful when building for different architectures or with different optimizations. However, only the variables described below are exported to the build environment. `GNUPGHOME' isn't described so I wouldn't expect it to be exported. I suppose it's stated as being `sourced', and makepkg(1) says it's a script, and looking at /usr/bin/makepkg shows it's a bash script, so you could whack an `export' in makepkg.conf too, but it would be nice if makepkg.conf(5) gave explicit approval to arbitrary environment variables if that's intended. -- Cheers, Ralph. https://plus.google.com/+RalphCorderoy