fix: GRUB_DISTRIBUTOR and grub install rectification

LP: 2034253 and LP: 2027686 both deal with buildd vm images failing to
boot when removing `--removable` and the stanzas copying EFI around. We
need to remove those stanzas for launchpad builder compatibility. even
though focal and jammy weren't failing, keeping everything aligned is
important. LP: 2034253 further showed that GRUB_DISTRIBUTOR being set by
default in grub requires lsb_release, which isn't in buildd images.
That's the root of why removing the stanzas failed. Since the only image
we know of where this bug is hit with grub is buildd (because everything
else has lsb_release), rather than adding a new dependency into buildd,
or backporting grub if we don't need to, setting GRUB_DISTRIBUTOR in the
buildd hook solves the immediate issue

live-build/buildd/hooks/02-disk-image-uefi.binary

@@ -98,39 +98,30 @@ install_grub() {
     # snap listings)
     chroot mountpoint dpkg-query -W > binary/boot/filesystem.packages
 
+    cat > mountpoint/etc/default/grub.d/50-builddimg-settings.cfg << EOF
+GRUB_DEFAULT=0
+GRUB_HIDDEN_TIMEOUT=0.1
+GRUB_HIDDEN_TIMEOUT_QUIET=true
+GRUB_TIMEOUT=0.1
+GRUB_CMDLINE_LINUX_DEFAULT="console=ttyS0"
+GRUB_RECORDFAIL_TIMEOUT=0
+GRUB_TERMINAL=console
+GRUB_DISTRIBUTOR=Ubuntu
+EOF
+
     chroot mountpoint grub-install "${loop_device}" \
         --boot-directory=/boot \
         --efi-directory=/boot/efi \
         --target=${efi_target} \
-        --removable \
         --uefi-secure-boot \
         --no-nvram
 
-    if [ -f mountpoint/boot/efi/EFI/BOOT/grub.cfg ]; then
-        sed -i "s| root| root hd0,gpt1|" mountpoint/boot/efi/EFI/BOOT/grub.cfg
-        sed -i "1i${IMAGE_STR}" mountpoint/boot/efi/EFI/BOOT/grub.cfg
-        # For some reason the grub disk is looking for /boot/grub/grub.cfg on
-        # part 15....
-        chroot mountpoint mkdir -p /boot/efi/boot/grub
-        chroot mountpoint cp /boot/efi/EFI/BOOT/grub.cfg /boot/efi/boot/grub
-    fi
-
     if [ "$ARCH" = "amd64" ]; then
         # Install the BIOS/GPT bits. Since GPT boots from the ESP partition,
         # it means that we just run this simple command and we're done
         chroot mountpoint grub-install --target=i386-pc "${loop_device}"
     fi
 
-    cat > mountpoint/etc/default/grub.d/50-builddimg-settings.cfg << EOF
-GRUB_DEFAULT=0
-GRUB_HIDDEN_TIMEOUT=0.1
-GRUB_HIDDEN_TIMEOUT_QUIET=true
-GRUB_TIMEOUT=0.1
-GRUB_CMDLINE_LINUX_DEFAULT="console=ttyS0"
-GRUB_RECORDFAIL_TIMEOUT=0
-GRUB_TERMINAL=console
-EOF
-
     divert_grub mountpoint
     chroot mountpoint update-grub
     replace_grub_root_with_label mountpoint