revert(glittershark): "Temporarily skip grfn's subtree"

This reverts commit 475d41f698. I'd like
my derivations back, please.

Changes necessary to get this working:

- Don't depend on `nixpkgs` being in the NIX_PATH for my website - it's
  not necessary anyway since emacs 27 is mainline now
- .skip-subtrees on things that shouldn't be evaluated anyway
- Get rid of system/pkgs, and move the one thing in there that *wasn't*
  already in third_party (alsi) to third_party
- Drop notifymuch for now - it's not working, and I'll probably get it
  landed in nixpkgs before I manage to get it working
- Add __readTree = true to my systems so they get built.
- explicitly disable ci for xanthous, which is failing to build and had
  been omitted previously

Change-Id: I20f5e81d6eb7ffe040091a08d75d0cb15304f707
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1864
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>

users/glittershark/system/home/modules/alsi.nix

@@ -1,8 +1,6 @@
 { config, lib, pkgs, ... }:
-let alsi = pkgs.callPackage ../../pkgs/alsi {};
-in
 {
-  home.packages = [ alsi ];
+  home.packages = [ config.lib.depot.third_party.alsi ];
 
   xdg.configFile."alsi/alsi.logo" = {
     source = ./nixos-logo.txt;

users/glittershark/system/home/modules/email.nix

@@ -36,26 +36,26 @@ in {
     msmtp
   ];
 
-  nixpkgs.overlays = [(self: super: {
-    notifymuch = self.python3Packages.callPackage ../../pkgs/notifymuch.nix {};
-  })];
+  # nixpkgs.overlays = [(self: super: {
+  #   notifymuch = self.python3Packages.callPackage ../../pkgs/notifymuch.nix {};
+  # })];
 
   systemd.user.services = mapAttrs' (name: account: {
     name = escapeUnitName "lieer-${name}";
     value.Service.ExecStart = mkForce "${pkgs.writeShellScript "sync-${name}" ''
       ${pkgs.gmailieer}/bin/gmi sync
-      ${pkgs.notifymuch}/bin/notifymuch
     ''}";
+    # ${pkgs.notifymuch}/bin/notifymuch
   }) accounts;
 
-  xdg.configFile."notifymuch/notifymuch.cfg".text = generators.toINI {} {
-    notifymuch = {
-      query = "is:unread and is:important";
-      mail_client = "";
-      recency_interval_hours = "48";
-      hidden_tags = "inbox unread attachment replied sent encrypted signed";
-    };
-  };
+  # xdg.configFile."notifymuch/notifymuch.cfg".text = generators.toINI {} {
+  #   notifymuch = {
+  #     query = "is:unread and is:important";
+  #     mail_client = "";
+  #     recency_interval_hours = "48";
+  #     hidden_tags = "inbox unread attachment replied sent encrypted signed";
+  #   };
+  # };
 
   accounts.email.maildirBasePath = "mail";
   accounts.email.accounts = mapAttrs (_: params@{ passEntry, ... }: {