Explicitly resolve mirror

I found that it otherwise sometimes fails to resolve in time when pacman needs it.
3 jobs for explicit-host in 12 minutes and 5 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Lint
passed shellcheck #5230

00:00:18

passed shfmt #5231

00:00:14

 
  Build
failed build #5232

00:11:46

 
Name Stage Failure
failed
build Build
du: cannot access 'output/*virtualbox*box': No such file or directory
Uploading artifacts for failed job
Uploading artifacts...
metrics.txt: found 1 matching files and directories

Uploading artifacts as "metrics" to coordinator... ok
id=5232 responseStatus=201 Created token=XyeBvHqs
Uploading artifacts...
build.env: found 1 matching files and directories

Uploading artifacts as "dotenv" to coordinator... ok
id=5232 responseStatus=201 Created token=XyeBvHqs
ERROR: Job failed: exit code 1