Cherry pick fix for unmatched boot image build fix from kinetic.

debian/changelog

@@ -1,3 +1,12 @@
+livecd-rootfs (2.765.6) UNRELEASED; urgency=medium
+
+  [ Alexandre Ghiti ]
+  * Fix SiFive Unmatched build. While merging the VisionFive support, we
+    removed the installation of u-boot-menu for the Unmatched by mistake
+    (LP: #1982735).
+
+ -- Łukasz 'sil2100' Zemczak <lukasz.zemczak@ubuntu.com>  Mon, 25 Jul 2022 10:24:08 +0200
+
 livecd-rootfs (2.765.5) jammy; urgency=medium
 
   * Add support for the VisionFive and the Nezha boards (LP: #1980935)

live-build/ubuntu-cpc/hooks.d/base/disk-image-uefi.binary

@@ -304,6 +304,9 @@ EOF
                         setup_cinocloud mountpoint
                         ;;
                     *)
+                        chroot mountpoint apt-get install -qqy u-boot-menu #grub-efi-riscv64
+                        efi_target=riscv64-efi
+                        chroot mountpoint u-boot-update
                         u_boot_arch="${SUBARCH}"
                         if [ "${u_boot_arch}" = "hifive" ]; then
                             u_boot_arch=sifive_fu540