Attempt nix-build instead of nixos-rebuild switch

I've encountered a few problems with attempting to support nixos-rebuild:
- the activation step requires `sudo` privileges
- the `buildkite-agent` runs on the same machine, socrates, that is rebuilding
  itself. This means that when the activation step runs, it will attempt to
  restart `buildkite-agent` when the agent is still working

I'm slowly removing places in my nix code that rely on '<bracket>' notation, so
that I no longer depend on NIX_PATH being set. I still have more work to do.

{covid-uk,sandbox}/default.nix are breaking when I attempt to run my
build-socrates.sh script locally, so I'm temporarily disabling them until I can
get CI working as I expect.

ci/scripts/build-socrates.sh

@@ -1,8 +1,6 @@
 set -euo pipefail
 
-nixos-rebuild \
+nix-build /home/wpcarro/nixpkgs/nixos \
-  -I nixos-config=/home/wpcarro/briefcase/nixos/socrates/configuration.nix \
+  -I nixos-config=/home/wpcarro/briefcase/nixos/socrates/default.nix \
-  -I nixpkgs=/home/wpcarro/nixpkgs \
+  -A system \
-  -I depot=/home/wpcarro/depot \
+  --show-trace
-  -I briefcase=/home/wpcarro/briefcase \
-  switch

nixos/socrates/default.nix

@@ -1,14 +1,6 @@
-{ ... }:
-
 let
-  # TODO(wpcarro): Instead of importing these dependencies as parameters that
+  briefcase = import /home/wpcarro/briefcase {};
-  # readTree will expose I need to import these dependencies manually because
-  # I'm building this using `nixos-rebuild`. When I better understand how to
-  # build socrates using readTree, prefer defining this as an anonymous
-  # function.
-  briefcase = import <briefcase> {};
   pkgs = briefcase.third_party.pkgs;
-
   trimNewline = x: pkgs.lib.removeSuffix "\n" x;
   readSecret = x: trimNewline (builtins.readFile ("/etc/secrets/" + x));
 in {
@@ -72,13 +64,7 @@ in {
   };
 
   nix = {
-    # Expose depot as <depot>, nixpkgs as <nixpkgs>
+    nixPath = [];
-    nixPath = [
-      "briefcase=/home/wpcarro/briefcase"
-      "depot=/home/wpcarro/depot"
-      "nixpkgs=/home/wpcarro/nixpkgs"
-    ];
-
     trustedUsers = [ "root" "wpcarro" ];
   };
 
@@ -229,16 +215,16 @@ in {
         enableACME = true;
         root = briefcase.website.blog;
       };
-      "sandbox.wpcarro.dev" = {
+      # "sandbox.wpcarro.dev" = {
-        addSSL = true;
+      #   addSSL = true;
-        enableACME = true;
+      #   enableACME = true;
-        root = briefcase.website.sandbox;
+      #   root = briefcase.website.sandbox;
-      };
+      # };
-      "learnpianochords.app" = {
+      # "learnpianochords.app" = {
-        addSSL = true;
+      #   addSSL = true;
-        enableACME = true;
+      #   enableACME = true;
-        root = briefcase.website.sandbox.learnpianochords;
+      #   root = briefcase.website.sandbox.learnpianochords;
-      };
+      # };
       "zoo.wpcarro.dev" = {
         addSSL = true;
         enableACME = true;

nixos/socrates/hardware.nix

@@ -5,7 +5,7 @@
 
 {
   imports =
-    [ <nixpkgs/nixos/modules/installer/scan/not-detected.nix>
+    [ /home/wpcarro/nixpkgs/nixos/modules/installer/scan/not-detected.nix
     ];
 
   boot.initrd.availableKernelModules = [ "ahci" "xhci_pci" "usbhid" "usb_storage" "sd_mod" "rtsx_pci_sdmmc" ];