Revert "Follow manual to build environment"

It does not apply overlays for dmenu and st, so stick to stackoverflow
solution for now.

This reverts commit 5308239b9a.

config.nix

@@ -1,25 +0,0 @@
-{
-  # Define packages to install.
-  # Provides convenient list for sharing and porting.
-  # Install via: nix-env -iA nixpkgs.myPackages
-  # See: https://nixos.org/manual/nixpkgs/stable/#sec-building-environment
-  packageOverrides = pkgs: with pkgs; {
-    myPackages = pkgs.buildEnv {
-      name = "my-packages";
-      paths = [
-        # System tools
-        pkgs.dmenu
-        pkgs.st
-        pkgs.dunst
-        pkgs.i3lock-color
-
-        # Dev tools
-        pkgs.litecli
-        pkgs.mkcert
-
-        # Media
-        pkgs.vlc
-      ];
-    };
-  };
-}

configuration.nix

@@ -0,0 +1,15 @@
+let
+  pkgs = import <nixpkgs> {};
+  inherit (pkgs) buildEnv;
+
+in buildEnv {
+  name = "my packages";
+  paths = [  ]
+    # System tools
+    ++ [ pkgs.dmenu pkgs.st pkgs.dunst pkgs.i3lock-color ]
+    # Dev tools
+    ++ [ pkgs.litecli pkgs.mkcert ]
+    # Media
+    ++ [ pkgs.vlc ]
+    ;
+}