nixos/bcc: init module

Looks trival, but it is easy to make the mistake
to add linuxPackages.bcc to systemPackages,
which breaks if the not the default kernel is used.

nixos/modules/module-list.nix

···
   ./programs/adb.nix
   ./programs/atop.nix
   ./programs/bash/bash.nix
+  ./programs/bcc.nix
   ./programs/blcr.nix
   ./programs/browserpass.nix
   ./programs/cdemu.nix

nixos/modules/programs/bcc.nix

···
+{ config, lib, pkgs, ... }:
+{
+  options.programs.bcc.enable = lib.mkEnableOption "bcc";
+
+  config = lib.mkIf config.programs.bcc.enable {
+    environment.systemPackages = [ config.boot.kernelPackages.bcc ];
+    boot.extraModulePackages = [ config.boot.kernelPackages.bcc ];
+  };
+}