amis: enable setting ami boot mode on registration

This is important since legacy bios mode is still the default for Intel
and AMD based instances on AWS. That is, even if your image is setup to
use UEFI on the OS level, the AMI will still use BIOS unless the boot
mode is explicitly set during registration.

nixos/maintainers/scripts/ec2/amazon-image.nix

@@ -4,6 +4,7 @@ with lib;
 
 let
   cfg = config.amazonImage;
+  amiBootMode = if config.ec2.efi then "uefi" else "legacy-bios";
 
 in {
 
@@ -106,10 +107,12 @@ in {
          --arg system ${lib.escapeShellArg pkgs.stdenv.hostPlatform.system} \
          --arg root_logical_bytes "$(${pkgs.qemu}/bin/qemu-img info --output json "$rootDisk" | ${pkgs.jq}/bin/jq '."virtual-size"')" \
          --arg boot_logical_bytes "$(${pkgs.qemu}/bin/qemu-img info --output json "$bootDisk" | ${pkgs.jq}/bin/jq '."virtual-size"')" \
+         --arg boot_mode "${amiBootMode}" \
          --arg root "$rootDisk" \
          --arg boot "$bootDisk" \
         '{}
           | .label = $system_label
+          | .boot_mode = $boot_mode
           | .system = $system
           | .disks.boot.logical_bytes = $boot_logical_bytes
           | .disks.boot.file = $boot
@@ -145,9 +148,11 @@ in {
          --arg system_label ${lib.escapeShellArg config.system.nixos.label} \
          --arg system ${lib.escapeShellArg pkgs.stdenv.hostPlatform.system} \
          --arg logical_bytes "$(${pkgs.qemu}/bin/qemu-img info --output json "$diskImage" | ${pkgs.jq}/bin/jq '."virtual-size"')" \
+         --arg boot_mode "${amiBootMode}" \
          --arg file "$diskImage" \
           '{}
           | .label = $system_label
+          | .boot_mode = $boot_mode
           | .system = $system
           | .logical_bytes = $logical_bytes
           | .file = $file

nixos/maintainers/scripts/ec2/create-amis.sh

@@ -275,6 +275,7 @@ upload_image() {
                 --region "$region" \
                 --architecture $amazon_arch \
                 --block-device-mappings "${block_device_mappings[@]}" \
+                --boot-mode $(read_image_info .boot_mode) \
                 "${extra_flags[@]}" \
                 | jq -r '.ImageId'
               )