Updated prepatched ISO generation command

patch-iso-debian script uses the mkisofs command
to generate an ISO. Some flags are used there to define
the El Torito configs, but one of these flags needs to be
updated in order to work in the LAT container.

Changes:
- Replaced the '-e' flag for '-eltorito-boot'
- Added '-eltorito-platform 0xEF' flag, following [1]
- Removed "-quiet" flag
- Added support for mkisofs backup option: xorrisofs

Note:
The mkisofs command available in the LAT container has
been customized in order to properly support El Torito
configs [2]. In order to execute patch-iso-debian outside
the LAT container, the developer can use cmds from the
xorriso package: either "xorrisofs" or "xorriso -as mkisofs" [3]

Ref:
[1] https://github.com/yoctoproject/poky/blob/master/scripts/lib/wic/plugins/source/isoimage-isohybrid.py#L424
[2] 19c6b9a324
[3] https://wiki.debian.org/RepackBootableISO

Test Plan: Generate and install pre-patched ISO produced
pass - Script ran inside LAT
pass - Script ran outside LAT

Story: 2011098
Task: 50217

Depends-On: https://review.opendev.org/c/starlingx/root/+/923771

Change-Id: I9c6b15b16385d3e2b4d385378211113d02438c23
Signed-off-by: Leonardo Fagundes Luz Serrano <Leonardo.FagundesLuzSerrano@windriver.com>

build-tools/patch-iso-debian

@@ -136,12 +136,12 @@ function check_requirements {
 
     # Declare "require reqA or reqB" as "reqA__reqB"
     local -a required_utils=(
-        7z                # p7zip-full
-        mkisofs           # genisoimage
-        isohybrid         # syslinux-utils
-        implantisomd5     # isomd5sum
-        ostree            # ostree
-        xmllint__python3  # libxml2-utils
+        7z                   # p7zip-full
+        mkisofs__xorrisofs   # genisoimage / xorriso
+        isohybrid            # syslinux-utils
+        implantisomd5        # isomd5sum
+        ostree               # ostree
+        xmllint__python3     # libxml2-utils / python3
     )
 
     local -i missing=0
@@ -265,26 +265,39 @@ fi
 echo "ISO Label: ${ISO_LABEL}"
 
 function pack_iso(){
-    # Repack the ISO
-    mkisofs -o "${OUTPUT_ISO}" \
-        -A "${ISO_LABEL}" -V "${ISO_LABEL}" \
-        -quiet -U -J -joliet-long -r -iso-level 2 \
-        -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot \
-        -boot-load-size 4 -boot-info-table \
-        -eltorito-alt-boot \
-        -e efi.img \
-        -no-emul-boot \
-        "${BUILDDIR}"
+    if (which xorrisofs &>/dev/null); then
+        PACK_ISO_CMD="xorrisofs"
+    else
+        PACK_ISO_CMD="mkisofs"
+    fi
+    echo "ISO packaging command: ${PACK_ISO_CMD}"
+
+    # Command Reference:
+    # https://github.com/yoctoproject/poky/blob/master/scripts/lib/wic/plugins/source/isoimage-isohybrid.py#L419
+
+    ${PACK_ISO_CMD} \
+        -V "${ISO_LABEL}" \
+        -o "${OUTPUT_ISO}" -U \
+        -J -joliet-long -r -iso-level 2 -b "isolinux/isolinux.bin" \
+        -c "isolinux/boot.cat" -no-emul-boot -boot-load-size 4 \
+        -boot-info-table -eltorito-alt-boot \
+        -eltorito-platform "0xEF" -eltorito-boot "efi.img" \
+        -no-emul-boot "${BUILDDIR}"
 
     isohybrid --uefi "${OUTPUT_ISO}"
     implantisomd5 "${OUTPUT_ISO}"
 }
 if ! pack_iso; then
+    if [ "${PACK_ISO_CMD}" = "mkisofs" ]; then
+        echo "NOTE: mkisofs has a customization in the LAT container to provide the '-eltorito-boot' flag."
+        echo "      To execute this script outside the LAT container, install the 'xorriso' package and run again."
+    fi
+
     echo "ERROR: Failed to build output ISO!"
     exit 1
 fi
 
-echo "Signing the .iso with the developer private key.."
+echo "Signing the .iso with the developer private key..."
 
 function sign_iso(){
     openssl dgst -sha256 \