Figure out an automated way to validate against new bootlibs

[geekosaur]

Probably yes; I forgot this time. I wonder if there's some way to automate this (we already have the appropriate inputs, but they can only be used with workflow_dispatch). Maybe a label, but then we need some way to pass it the appropriate inputs.

Originally posted by @geekosaur in #11127 (comment)

[TeofilC]

IIRC https://discourse.haskell.org/t/dependency-bound-bumping-using-renovate/11397 does something like this. Where it adds like a special footer to the commit that your CI can then pick up and add the constraint