Move CPU optimizations into their own role.

This is remove duplication between the individual hosts folders.

nix/configuration/configuration.nix

@@ -44,6 +44,7 @@
     ./roles/nix_index
     ./roles/nix_worker
     ./roles/nvme
+    ./roles/optimized_build
     ./roles/pcsx2
     ./roles/python
     ./roles/qemu
@@ -84,6 +85,16 @@
   # Use nixos-rebuild-ng
   # system.rebuild.enableNg = true;
 
+  # Keep outputs so we can build offline.
+  nix.extraOptions = ''
+    keep-outputs = true
+    keep-derivations = true
+  '';
+
+  # Technically only needed when building the ISO because nix detects ZFS in the filesystem list normally. I basically always want this so I'm just setting it to always be on.
+  boot.supportedFilesystems.zfs = true;
+  # TODO: Is this different from boot.supportedFilesystems = [ "zfs" ]; ?
+
   services.getty = {
     autologinUser = "talexander"; # I use full disk encryption so the user password is irrelevant.
     autologinOnce = true;