refactor(gs/home): Move rebuild-mugwump script to all machines

Chupacabra doesn't even exist anymore, plus I want this installed on all
home systems

Change-Id: Id0e5c89797b1ad52b2a24d60ad3ab5e125f60266
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2696
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI

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

@@ -44,6 +44,16 @@
     nix-prefetch-github
     nix-review
     cachix
+    (writeShellScriptBin "rebuild-mugwump" ''
+      set -eo pipefail
+      cd ~/code/depot
+      nix build -f . users.glittershark.system.system.mugwumpSystem -o /tmp/mugwump
+      nix copy -f . users.glittershark.system.system.mugwumpSystem \
+        --to ssh://mugwump
+      system=$(readlink -ef /tmp/mugwump)
+      ssh mugwump sudo nix-env -p /nix/var/nix/profiles/system --set $system
+      ssh mugwump sudo $system/bin/switch-to-configuration switch
+    '')
   ];
 
   programs.ssh = {