bug#46942: ci.guix.gnu.org is slow from my system

[raid5atemyhomework via Bug reports for GNU Guix <bug-guix@gnu.org>]

> * Is there a way to make `guix-daemon` use a Tor proxy?  I have two systems using Guix, one is a Guix System, the other is using a foreign distro, and I'd like to adjust both to use Tor instead since it's faster.

I saw that `guix-daemon` respects `http_proxy` and `https_proxy` envvars, but trying it out on my foreign-distro Guix computer, adding `https_proxy=socks5h://127.0.0.1:9050 http_proxy=socks5h://127.0.0.1:9050` to the `systemd` service file doesn't work.

```
guix substitute: error: TLS error in procedure 'handshake': The TLS connection was non-properly terminated.
substitution of /gnu/store/1bdldr80p39g1mjnh76xw6hmwqrrb8lz-wine64-6.0 failed
guix package: error: some substitutes for the outputs of derivation `/gnu/store/wr9kf2bgcsvwxcmhnl9lf047nr8xcklc-wine64-6.0.drv' failed (usually happens due to networking issues); try `--fallback' to build derivation from source
```
Looking at the foreign distro's syslog:

```
Mar  5 19:52:03 developer guix-daemon[145182]: accepted connection from pid 145190, user raid5atemyhomework
Mar  5 19:52:05 developer guix-daemon[145200]: spurious SIGPOLL
Mar  5 19:52:07 developer Tor[1029]: Socks version 67 not recognized. (This port is not an HTTP proxy; did you want to use HTTPTunnelPort?)
```

So it looks to me that `guix-daemon` expects `https_proxy` to be an HTTPS proxy and not a SOCKS5/SOCKS5H proxy. I'll look into Tor's HTTPTunnelPort.

Thanks
raid5atemyhomework