spotlights-macbook-air: Enable SMBIOS generation in U-Boot

libvirtd would otherwise fail attempting to execute dmidecode. That's an issue in itself, but it's far easier to just simply enable SMBIOS support than maintain patches against libvirtd.

hosts/linux/spotlights-macbook-air/configuration.nix

@@ -34,6 +34,50 @@
     };
   };
 
+  nixpkgs.overlays = [
+    # We need SMBIOS generation enabled for libvirtd,
+    # as it otherwise stumbles over executing dmidecode.
+    (final: prev: {
+      uboot-asahi = prev.uboot-asahi.overrideAttrs (old: {
+        # TODO(spotlightishere): It'd be far more ideal to actually override.
+        # However, somehow overriding extraConfig seems to coerce things into a string.
+        # We wholly override it here, and thus should monitor to see if it changes upstream.
+        extraConfig = ''
+          # Upstream
+          CONFIG_IDENT_STRING=" ${old.version}"
+          CONFIG_VIDEO_FONT_4X6=n
+          CONFIG_VIDEO_FONT_8X16=n
+          CONFIG_VIDEO_FONT_SUN12X22=n
+          CONFIG_VIDEO_FONT_16X32=y
+          CONFIG_CMD_BOOTMENU=y
+
+          # Custom modifications
+          CONFIG_SMBIOS=y
+          CONFIG_GENERATE_SMBIOS_TABLE=y
+        '';
+      });
+    })
+  ];
+
+  # As recommended in https://nixos.wiki/wiki/Libvirt#Setup
+  virtualisation.libvirtd = {
+    enable = true;
+    qemu = {
+      package = pkgs.qemu_kvm;
+      runAsRoot = true;
+      swtpm.enable = true;
+      ovmf = {
+        enable = true;
+        packages = [
+          (pkgs.OVMF.override {
+            secureBoot = true;
+            tpmSupport = true;
+          }).fd
+        ];
+      };
+    };
+  };
+
   environment.systemPackages = with pkgs; [
     legcord
     vscode