Set up hosted Jenkins

[alexlist]

We have a free FOSS cloudbees subscription. Configure hosted Jenkins on cloudbees for building openwrt-deps, OpenWRT buildroot, and images.

Ensure Jenkins config can be repurposed in case we need to migrate to different or own Jenkins infra

[nbraud]

I'm trying to configure this piece of crap.

[nbraud]

Ok, I currently have several issues:

1. the GitHub integration (hooks to react on pushes and pull requests) isn't working;
2. I can't find a way not to make it use the small EC2 instances.

I'm trying to mitigate 1 by setting up SCM polling. Will see if it works.
2 is still a blocker. At that point, I'm willing to give another CI system a try.

[nbraud]

https://ffgraz.ci.cloudbees.com/job/OpenWRT/7/console shows the polling works.