haskell.compiler.ghc94: Backport PPC64 ELFv2 support

[OPNA2608]

Extracted from #462247

ghc94s build, but don't run.

puna@Yubel ~> /nix/store/dhv857lm0ahyfbg7np9jprg5j0b9nkz1-ghc-powerpc64-unknown-linux-gnuabielfv1-9.4.8/bin/ghci
fish: Job 1, '/nix/store/dhv857lm0ahyfbg7np9j…' terminated by signal SIGSEGV (Address boundary error)
puna@Yubel ~ [SIGSEGV]> /nix/store/p5s6ai4z34m72qr30174vwbdcq6qhc26-ghc-powerpc64-unknown-linux-gnuabielfv2-9.4.8/bin/ghci
fish: Job 1, '/nix/store/p5s6ai4z34m72qr30174…' terminated by signal SIGSEGV (Address boundary error)
puna@Yubel ~ [SIGSEGV]> /nix/store/lfqpkyr81rld6sb25z8h8lzhisssh88m-ghc-musl-powerpc64-unknown-linux-musl-9.4.8/bin/ghci
fish: Job 1, '/nix/store/lfqpkyr81rld6sb25z8h…' terminated by signal SIGSEGV (Address boundary error)

Identical to current behaviour of ppc64-elfv1 on master. I'm not gonna try it, but flipping enableUnregisterised to true might fix them. Noted in #439258 (comment), I think the suitability of cross-compiled ghc94 is still getting looked into though?

I'm unsure about the patch for GHC 9.4, if we can't verify that it works. Should we postpone that until these run in the first place?

Seems like ppc64le has similar issues with cross-compiled registerised GHC segfaulting. Maybe a general issue on (64-bit) POWER? #439258 (comment)

I'm fine with pulling the GHC 9.4 changes out for now until they're actually needed (bootstrapping off of cross-compiled GHC).

Things done

• Built on platform:
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• Tested, as applicable:
  • NixOS tests in nixos/tests.
  • Package tests at passthru.tests.
  • Tests in lib/tests or pkgs/test for functions and "core" functionality.
• Ran nixpkgs-review on this PR. See nixpkgs-review usage.
• Tested basic functionality of all binary files, usually in ./result/bin/.
• Nixpkgs Release Notes
  • Package update: when the change is major or breaking.
• NixOS Release Notes
  • Module addition: when adding a new NixOS module.
  • Module update: when the change is significant.
• Fits CONTRIBUTING.md, pkgs/README.md, maintainers/README.md and other READMEs.

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