GHC 9.12.3 is now available

[juhp]

@juhp

the gtk2hs stack had to be disabled due toerror: ‘runIO_closure’ undeclared

I guess this is fallout from rts: Avoid static symbol references to ghc-internal (ecc03b62) · Commits · Glasgow Haskell Compiler / GHC · GitLab - though I don’t see it mentioned in the relnotes (see also !14892).