zig: refactor system env substitution

  # Zig's build looks at /usr/bin/env to find dynamic linking info. This doesn't

  # work in Nix's sandbox. Use env from our coreutils instead.

  postPatch =

    (

    let

      zigSystemPath =

        if lib.versionAtLeast finalAttrs.version "0.12" then

        ''

          substituteInPlace lib/std/zig/system.zig \

            --replace-fail "/usr/bin/env" "${coreutils}/bin/env"

        ''

          "lib/std/zig/system.zig"

        else

          "lib/std/zig/system/NativeTargetInfo.zig";

    in

    ''

          substituteInPlace lib/std/zig/system/NativeTargetInfo.zig \

            --replace-fail "/usr/bin/env" "${coreutils}/bin/env"

      substituteInPlace ${zigSystemPath} \

        --replace-fail "/usr/bin/env" "${lib.getExe' coreutils "env"}"

    ''

    )

    # Zig tries to access xcrun and xcode-select at the absolute system path to query the macOS SDK

    # location, which does not work in the darwin sandbox.

    # Upstream issue: https://github.com/ziglang/zig/issues/22600