feat: use fenix for cargo, add dynamic linking and pkg-config paths

nix/modules/rust.nix

@@ -0,0 +1,41 @@
+{
+  pkgs,
+  lib,
+  config,
+  inputs,
+  ...
+}:
+{
+  options.rust = {
+    enable = lib.mkEnableOption "enable rust" // {
+      default = true;
+    };
+  };
+
+  config = lib.mkIf config.rust.enable {
+    nixpkgs.overlays = [ inputs.fenix.overlays.default ];
+    environment.systemPackages = with pkgs; [
+      (pkgs.fenix.stable.withComponents [
+        "cargo"
+        "clippy"
+        "rust-src"
+        "rustc"
+        "rustfmt"
+      ])
+      openssl
+      pkgconf
+    ];
+    environment.variables = {
+      PKG_CONFIG_PATH =
+        with pkgs;
+        lib.makeSearchPath "/lib/pkgconfig" [
+          openssl.dev
+        ];
+      LD_LIBRARY_PATH = "/run/current-system/sw/share/nix-ld/lib";
+    };
+    programs.nix-ld.libraries = with pkgs; [
+      openssl
+      zlib
+    ];
+  };
+}