A better fix than in 104448e75d, hence a
revert + the fix.
It turns out that this commit has the side-effect that when having e.g.
`StrictHostKeyChecking=accept-new` for a remote builder, the warnings à la
Warning: Permanently added 'builder' (ED25519) to the list of known hosts.
actually end up in the derivation's log whereas hostkey verification
errors don't, but only in the stderr of the `nix-build` invocation
(which was the motivation for the patch).
This change writes the stderr from the build-hook to
* the daemon's stderr, so that the SSH errors appear in the journal
(which was the case before 104448e75d)
* the client's stderr, as a log message
* NOT to the drv log (this is handled via `handleJSONLogMessage`)
I tried to fix the issue for legacy-ssh as well, but failed and
ultimately decided to not bother.
I know that we'll sooner or later replace the entire component, however
this is the part of the patch I have working for a while, so I figured I
might still submit it for the time being.
Change-Id: I21ca1aa0d8ae281d2eacddf26e0aa825272707e5
Maximilian Bosch
4682e40183