Configure /etc/installurl

[dentarg]

I think it would be good to configure the box with https://ftp.lysator.liu.se/pub/OpenBSD as the installurl(5) as the default one removes packages for older versions:

openbsd71$ sudo pkg_add -z "python%3"
https://cdn.openbsd.org/pub/OpenBSD/7.1/packages/amd64/: no such dir
Can't find python%3
openbsd71$ cat /etc/installurl
https://cdn.openbsd.org/pub/OpenBSD

[dentarg]

It is possible to configure at box build time with the mirror variable:

boxes/openbsd/template.json

Lines 2 to 10 in 89b8c0e

	"variables": {
	"ftp_proxy": "{{env `ftp_proxy`}}",
	"http_proxy": "{{env `http_proxy`}}",
	"https_proxy": "{{env `https_proxy`}}",
	"mirror": "https://fastly.cdn.openbsd.org",
	"boot_wait": "30s",
	"major_version": "7",
	"minor_version": "3"
	},

https://developer.hashicorp.com/packer/guides/hcl/variables#command-line-flags