main.star: enable misccompile builders as trybots

They're working and passing everywhere now.

Keep them around as post-submit builders too, at least for now. This is
so that if something regresses, it's easy to see. We can make them only
run as trybots once LUCI trybots are required to run on each CL, likely
after old trybots are turned off too, since they may not catch all that
the new ones do. We'll see.

Fixes golang/go#61698.

Change-Id: I8e0e531eb51ec5387aafa350ee4dc0009ce76d65
Reviewed-on: https://go-review.googlesource.com/c/build/+/518800
TryBot-Bypass: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Heschi Kreinick <[email protected]>
Auto-Submit: Dmitri Shuralyov <[email protected]>

Author: dmitshur