Use curl instead of git

6 jobs for nix-ci in 10 seconds (queued for 3 seconds)
Name Stage Failure
common Prepare There is an unknown failure, please try again
 using the --cacert option.
If this HTTPS server uses a certificate signed by a CA represented in
the bundle, the certificate verification probably failed due to a
problem with the certificate (it might be expired, or the name might
not match the domain name in the URL).
If you'd like to turn off curl's verification of the certificate, use
the -k (or --insecure) option.
HTTPS-proxy has similar options --proxy-cacert and --proxy-insecure.
ERROR: Job failed: exit code 1