fnginstall-postinstallation: Fix boot partition detection for fngsystem

The scripts failed if run in an installed fngsystem. This is needed in
FT2, when new xml files are installed after the FNGSystem installation.

(cherry picked from commit 920b5c91)

recipes-bsp/fng-install/prepare-image/gf-prepare-common.sh

@@ -5,6 +5,7 @@
 # List of possible bootpartitions for this installation.
 # Its possibly changed during installation
 BOOTPARTITIONS="/dev/disk/by-label/LINUX /dev/mmcblk0p2 /dev/mmcblk1p2"
+BOOTPARTITIONS_FNG="/dev/disk/by-label/Flash-N-Go /dev/mmcblk0p1 /dev/mmcblk1p1"
 BOOTSCRIPTNAMES="boot.cfg bootB.cfg boot-alt.cfg"
 
 error_out()
@@ -206,8 +207,36 @@ get_platform()
     return 0
 }
 
+# =================================================================
+# Functions to find out if we are inside fngsystem
+#
+# =================================================================
+
+is_fng_system_gfversion()
+{
+    # gfversion return 0 if the version can be correctly found
+    # and an error otherwise
+    gf-versions.sh -q fngsystem 2>/dev/null && return 0
+    return 1
+}
+is_fng_system_deprecated()
+{
+    # if the hostname contains 'FLASH-N-GO', return 0
+    grep -q FLASH-N-GO /etc/hostname && return 0
+    return 1
+}
+
 # Allow to debug commands
 VERBOSE="${VERBOSE:-0}"
-if [ "$VERBOSE" -gt 2 ];then
+if [ "$VERBOSE" -ge 2 ];then
     set -x
 fi
+if command -v gf-versions.sh 1>/dev/null;then
+    is_fng_system=is_fng_system_gfversion
+else
+    is_fng_system=is_fng_system_deprecated
+fi
+if $is_fng_system; then
+    BOOTPARTITIONS=$BOOTPARTITIONS_FNG
+fi
+