OMR: Jenkins no known_hosts entry for github.com on built-in node
Summary
One of our build pipelines (z/os) uses an ssh url for the repo to clone because https doesn't work. After the upgrade last week, the part on the Controller that grabs the jenkinsfile (lightweight checkout) is failing because it doesn't trust github.com
stderr: No ECDSA host key is known for github.com and you have requested strict checking.
Host key verification failed.
fatal: Could not read from remote repository.
https://ci.eclipse.org/omr/job/Build-zos_390-64/2187/console
Started failing last wed (Aug 17) between 10:00am and 11:30pm EST. Last passed build was technically number 2174. Failing from 2175 onward.
We could avoid this by using an https url in the job config (See build 2188. Or any other platform). But that url is passed to the scm in the job running on the static zos node and will fail if it's https. We could convert it on the fly but that's a hack in my opinion.
We should be able to add the known_hosts entry on the Controller and it should work again. I'm not sure why it stopped working though. Might be worth determining the root cause while we're here.