Enable GHA "Checks" for 17u

[Aleksey Shipilev]

Hi,

JDK 17u workspace has GHA workflows enabled, so it can be tested.

For example, this is the run for recent backport:
   https://github.com/shipilev/jdk17u/actions/runs/1158027935

However, the "Checks" tab in PR does not show it:
   https://github.com/openjdk/jdk17u/pull/35

I believe it requires a bit of configuration nudge (in 17u Skara bots?).
Christoph, do you remember what you did in 11u for this?
Rob, can you see what can be done here?

-- 
Thanks,
-Aleksey