add uefi package and iso builder

thanks to https://github.com/martiert/x13s-bios

packages/uefi-usbiso.nix

@@ -0,0 +1,50 @@
+{
+  stdenv,
+  parted,
+  util-linux,
+  dosfstools,
+  mtools,
+  uefi,
+}:
+
+stdenv.mkDerivation rec {
+  name = "usbdisk";
+  version = uefi.version;
+
+  src = ./.;
+
+  nativeBuildInputs = [
+    parted
+    util-linux
+    dosfstools
+    mtools
+  ];
+
+  doUnpack = false;
+  buildPhase = ''
+    img=${name}-${version}.iso
+    gap=8
+    blocks=$(du -B 512 --summarize --apparent-size ${uefi} | awk '{ print $1 }')
+    blocks=$(( 2 * blocks ))
+    size=$(( 512 * blocks + gap * 1024 * 1024 + 34*512))
+    truncate -s $size $img
+    sfdisk $img <<EOF
+      label: gpt
+      start=''${gap}M, size=$blocks, type=uefi
+    EOF
+
+    eval $(partx $img -o START,SECTORS --nr 1 --pairs)
+    truncate -s $(( SECTORS * 512 )) part.img
+    mkfs.vfat part.img
+    mcopy -spvm -i ./part.img ${uefi}/EFI "::/EFI"
+    mcopy -spvm -i ./part.img ${uefi}/Flash "::/Flash"
+
+    dd conv=notrunc if=part.img of=$img seek=$START count=$SECTORS
+    rm -fr part.img
+  '';
+
+  installPhase = ''
+    mkdir $out
+    mv ${name}-${version}.iso $out/
+  '';
+}