fix: Ensure required dependencies are installed before trying `grub-install` (LP: #2031640)

As a result of not installing recommended packages the packages required to run `grub-install`
are no longer installed by default.

To ensure we can successfully run `grub-install` we install both `grub-pc` and `grub2-common`
packages.

debian/changelog

@@ -2,6 +2,7 @@ livecd-rootfs (23.10.16) mantic; urgency=medium
 
   * fix: Do not install recommends for ubuntu-cpc minimized project (LP: #2031640)
   * fix: Remove dangling symlink /boot/initrd.img.old if exists (LP: #2031640)
+  * fix: Ensure required dependencies are installed before trying `grub-install` (LP: #2031640)
 
  -- Philip Roche <phil.roche@ubuntu.com>  Thu, 17 Aug 2023 11:44:23 +0100
 

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

@@ -115,6 +115,8 @@ esac
 
 if [ "${should_install_grub}" -eq 1 ]; then
     echo "(hd0) ${loop_device}" > mountpoint/tmp/device.map
+    # install the required package to get the grub-install command
+    chroot mountpoint apt-get -qqy install --no-install-recommends grub-pc grub2-common
     chroot mountpoint grub-install ${loop_device}
     chroot mountpoint grub-bios-setup \
         --boot-image=i386-pc/boot.img \