recv_gpg_keys: use another key server than keys.gnupg.net

[Chih-Hsuan Yen]

Currently, recv_gpg_keys tries hkp://keys.gnuph.net. That domain is not a real domain name but a hard-coded mapping in gnupg. Currently, the build server has gnupg-2.2.28, in which hkp://keys.gnupg.net is mapped to hkp://hkps.pool.sks-keyservers.net, and the latter is gone. As a result, fetching GPG keys may fail:

gpg: 从公钥服务器接收失败：无名称

gnupg-2.2.29 updates the mapping to a working server, so a short term fix can be updating rge server. In the long term, I suggest to switch to another key server, so that debugging GPG issues is easier, and development of GnuPG will not affect lilac.

[依云]

Thanks. I didn't know that it's not a real server.

[Chih-Hsuan Yen]

Thanks! I didn't know that until yesterday, either :P