Adds external bootloader drive to sol config.

The device is currrently a placeholder ID, another commit will replace
it with the right one.

systems/x86_64-linux/sol/disk-config.nix

@@ -21,6 +21,19 @@
     };
 
     disk = {
+      boot = {
+        device = "/dev/disk/by-id/usb-0000";
+        type = "disk";
+        content = {
+          type = "table";
+          format = "msdos";
+
+          # No partitions, this is a flash drive to just store the bootloader
+          # because SuperMicro's BIOS doesn't support legacy boot from the
+          # storage backplane for some reason.
+          partitions = [];
+        };
+      };
       osdisk = {
         device = "/dev/disk/by-id/ata-ST9500420AS_5VJCBJ3C";
         type = "disk";

systems/x86_64-linux/sol/hardware.nix

@@ -22,7 +22,7 @@
 
   boot.loader.grub = {
     enable = true;
-    device = config.disko.devices.disk.osdisk.device;
+    device = config.disko.devices.disk.boot.device;
     efiSupport = false;
     gfxmodeBios = "auto";
     configurationLimit = 5;