So this works (gpg --armor --clear-sign):
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512
test
-----BEGIN PGP SIGNATURE-----
iHUEARYKAB0WIQRve2u5qbYyVV4aA8Eyrx85xO4D8gUCXuvw0wAKCRAyrx85xO4D
8opLAQDK5Spug8MTQuocZj0PUllamGtcdLzd72xraeg5IfnVngD9H8eXUfSjkTB4
0hHQUL6+tZruzw18gStuMMLNoE2utAY=
=6NcD
-----END PGP SIGNATURE-----