Bundling doesn't include runtime dependencies

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I’m trying to bundle a Zig project that uses mach. Building works perfectly (even when cross-compiling), but the bundle output (standalone binary) doesn’t seem to include the runtime dependencies, unlike the build output, which has a proper launcher script that accounts for these.

For instance, the wrapped program from nix build .#packages.x86_64-linux.x86_64-linux-gnu includes these libs from the store too, and I can’t find these strings anywhere in the bundled program created by nix bundle .#packages.x86_64-linux.x86_64-linux-gnu:

alsa-lib-1.2.9/lib
libXinerama-1.1.5/lib
libXrandr-1.5.4/lib
libXrender-0.9.11/lib
libXi-1.8.1/lib
libXfixes-6.0.1/lib
libXext-1.3.5/lib
libX11-1.8.7/lib
libGL-1.7.0/lib
vulkan-loader-1.3.268.0/lib

Minimal flake.nix:

{
  description = "zenui";

  inputs = {
    self = {
      type = "git";
      url = "https://github.com/thinnerthinker/zenui.git";
      rev = "19d6d20ce327a02e88eee88939cbf257b7c6d602";
    };
    mach.url = "github:Cloudef/mach-flake?rev=047c0fa57b7650d69a6fa199a4d93fe0a08c3938";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, mach, flake-utils, ... }:
    let
      allTargetTriples = [
        "x86_64-windows-gnu"
        "aarch64-linux-gnu"
        "x86_64-linux-gnu"
        "aarch64-darwin"
        "x86_64-darwin"
      ];
    in
    flake-utils.lib.eachDefaultSystem (system:
      let
        env = mach.outputs.mach-env.${system} { };
        system-triple = env.lib.zigTripleFromString system;
      in
      with builtins; rec {
        packages = env.pkgs.lib.genAttrs allTargetTriples (targetTriple: env.packageForTarget targetTriple {
          name = "zenui";
          src = self;
          buildInputs = with env.pkgsForTarget targetTriple; [ ];
          zigPreferMusl = false;
          zigDisableWrap = false;
          zigBuildFlags = [ "-Doptimize=ReleaseSmall" ];
        });
      });
}

Nix version: 2.18.1
NixOS version: 23.11.20240328.219951b (Tapir)