Undefined symbol when using zigler and C file

This my first time using zig and zigler.

I am trying to use the embedded library for wireguard.
I have in the same folder, wireguard.h, wireguard.c and wireguard.ex.
The Wireguard module has

defmodule Wireguard do
  use Zig,
    otp_ap: :wg_man,
    c_src: [{"wireguard.c", ["-Wall"]}],
    include_dir: "."

  ~Z"""
  const std = @import("std");
  const crypto = std.crypto;
  const log = std.log.scoped(.wireguard);

  const wireguard = @cImport({
    @cInclude("wireguard.h");
  });

  pub fn list_devices() void {
    var deviceNames: [*c]u8 = null;
 
   deviceNames = wireguard.wg_list_device_names() orelse null;

    defer std.c.free(@ptrCast(?*anyopaque, deviceNames));

    if (deviceNames == null) {
        log.err("Unable to get device names", .{});
        return;
    }
  }
  """

When I try to mix compile, I get the following error:

== Compilation error in file lib/wireguard/wireguard.ex ==
** (MatchError) no match of right hand side value: ["error: ld.lld: undefined symbol: wg_list_device_names\n    note: referenced by .Elixir.Wireguard.zig:13 (/home/herman/Projects/wg_man/lib/wireguard/.Elixir.Wireguard.zig:13)\n    note:               /home/herman/.cache/zig/o/f3cd82336c77b73ffaead67d9007ba46/sema.o:(.Elixir.Wireguard.list_devices)"]
    (zigler 0.10.2) lib/zig/compile_error.ex:11: Zig.CompileError.to_error/2
    (zigler 0.10.2) lib/zig/sema.ex:88: Zig.Sema.run_sema!/3
    (zigler 0.10.2) lib/zig/compiler.ex:76: Zig.Compiler.compile/4
    (zigler 0.10.2) expanding macro: Zig.Compiler.__before_compile__/1
    lib/wireguard/wireguard.ex:1: Wireguard (module)

This function is defined in wireguard.c, so why is it not being found?
If I remove the body from the zig function it compiles and when I look at the exported functions in the generated Elixir.Wireguard.so I do find all the functions there.
I am probably missing something, but I have no clue where to start looking.