pkgs/stdenv/linux: add powerpc64 bootstrap files

[minijackson]

Description of changes

Adds powerpc64 bootstrap files to linux' stdenv, so that nixpkgs is usable from a powerpc64 machine, or using emulatedSystems = [ "powerpc64-linux" ];.

I'm not sure I got the hashes right the first time, so they might need to be updated the tarballs are uploaded. I'm not sure how to test it while we are missing the uploads.

Things done

• Built on platform(s)
  • emulated system
  • native
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
• Fits CONTRIBUTING.md.

[r-burns]

Until these are uploaded to tarballs.nixos.org, please use working URLs for ease of testing/verification. Then once we get someone to do the upload, we can change the URLs to point to tarballs.nixos.org and verify that the hashes are the same before merging.

[minijackson]

so after 12h of compilation, Nix started to compile the "real" gcc, but it failed with this output, apparently because the C preprocessor isn't there/detected? But it succeeded in compiling bison, gettext, perl, and other things, so it could be a bug elsewhere, but I'm not sure where.

On another note, would it be possible to replace the value of system by the config config on in nixpkgs systems attrset? Right now cross-compiling for powerpc64-linux and powerpc64-unknown-linux-gnu leads to two different builds of gcc and the rest, to my knowledge only because the name differs.

[minijackson]

Closing as I no longer have a use for it, if someone is interested, feel free to re-open or tag me on another PR.