ghostty: limit the amount of build cores (#446056)

  pandoc,

  pkg-config,

  removeReferencesTo,

  util-linux,

  versionCheckHook,

  wrapGAppsHook4,

  writeShellApplication,

  zig_0_14,

  # Usually you would override `zig.hook` with this, but we do that internally

}:

let

  zig = zig_0_14;

  zig_hook = zig.hook.overrideAttrs {

  # HACK:

  # Work around a Zig bug where embedding a large enough file could crash

  # the compiler when too many cores are used, which causes Hydra builds to

  # reliably fail. See these links for more info:

  #

  #  * https://github.com/ziglang/zig/issues/25297

  #  * https://github.com/ziglang/zig/issues/22867

  #  * https://github.com/ghostty-org/ghostty/discussions/8676

  #

  # Note that the `-j` parameter does NOT fix this. It seems like the faulty

  # intern pool logic always depends on the full amount of available cores

  # instead of the value of `-j`, so we have to use `taskset` to trick Zig

  # into thinking it only has access to a limited amount of cores.

  zigWithLimitedCores = writeShellApplication {

    name = "zig";

    passthru = {

      inherit (zig) version meta;

    };

    runtimeInputs = [

      zig

      util-linux

    ];

    text = ''

      maxCores=$(nproc)

      # 32 cores seem to be the upper limit through empiric testing

      coreLimit=$((maxCores < 32 ? maxCores : 32))

      # Also take NIX_BUILD_CORES into account so the build respects the `--cores` argument

      effectiveCores=$((NIX_BUILD_CORES > coreLimit ? coreLimit : NIX_BUILD_CORES))

      taskset -c "0-$((effectiveCores - 1))" zig "$@"

    '';

  };

  zig_hook =

    (zig.hook.override {

      zig = zigWithLimitedCores;

    }).overrideAttrs

      {

        zig_default_flags = "-Dcpu=baseline -Doptimize=${optimizeLevel} --color off";

      };

in