nix: migrate more packages into the overlay

nix/home-manager/profiles/common.nix

@@ -7,25 +7,13 @@ in {
   programs.home-manager.enable = true;
   programs.home-manager.path = https://github.com/rycee/home-manager/archive/master.tar.gz;
 
+  nixpkgs.overlays = [
+    (import ../../overlay.nix)
+  ];
+
   nixpkgs.config = {
     allowBroken = true;
     allowUnfree = true;
-
-    # TODO: move this to a pkgs overlay
-    packageOverrides = pkgs: with pkgs; {
-      busyboxStatic =  busybox.override {
-        enableStatic = true;
-        extraConfig = ''
-           CONFIG_STATIC y
-           CONFIG_INSTALL_APPLET_DONT y
-           CONFIG_INSTALL_APPLET_SYMLINKS n
-         '';
-      };
-
-      dropbearStatic = dropbear.override {
-        enableStatic = true;
-      };
-    };
   };
 
   home.keyboard = {