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/default.nix

@@ -10,7 +10,7 @@ rec {
     sha256 = "10svwspmsf46rijzsh0h9nmz1mq2998wcml8yp36mwksgi8695pc";
   });
 
-  home = confPath: import "${home-manager}/modules" {
+  home = confPath: (import "${home-manager}/modules" {
     pkgs = nixpkgs;
     configuration = { config, lib, ... }: {
       imports = [confPath];
@@ -20,7 +20,7 @@ rec {
 
       lib.depot = depot;
     };
-  };
+  }) // { __readTree = true; };
 
   chupacabra = home ./machines/chupacabra.nix;
 }