Tools to ease nuttx config maintenance (#6452)

* Added tool to restore defconfig sections after make [old|menu]config

* Use tool to restore defconfig sections after make [old|menu]config

   invocation:
      make px4fmu-v2_default oldconfig_px4fmu-v2
      make px4fmu-v2_default menuconfig_px4fmu-v2

Tools/nuttx_defconf_tool.sh

@@ -0,0 +1,48 @@
+#! /bin/bash
+
+if [ $# -eq 0 ]
+  then
+    echo "Usage: $0 <path to defconfig>"
+    exit 1
+fi
+configsdir=nuttx-configs
+defconf=$1
+configsrc=$configsdir${defconf##*$configsdir}
+
+if [ ! -f  $defconf ]
+  then
+    echo "$defconf does not exist"
+    exit 2
+fi
+
+
+lastconf=$defconf.last
+chunk=$defconf.chunk
+
+echo $configsrc
+git show HEAD:$configsrc > $lastconf
+
+lead='^# Board Selection$'
+tail='^# Common Board Options$'
+
+cat $lastconf | sed -n "/$lead/,/$tail/p" | sed '1d;$d' > $chunk
+
+echo "Fix up Board Selection"
+sed -i -e "/$lead/,/$tail/{ /$lead/{p; r $chunk
+        }; /$tail/p; d }" $defconf
+
+
+if grep --quiet CONFIG_START_YEAR $lastconf ; then
+  lead='^CONFIG_START_YEAR='
+  tail='^CONFIG_START_DAY='
+  cat $lastconf | sed -n "/$lead/,/$tail/p" > $chunk
+  lead='^# Clocks and Timers$'
+  echo "Fix up Clocks and Timers"
+  sed -i -e "/$lead/{N;{r $chunk
+    }}" $defconf
+else
+ echo not found
+fi
+
+rm $lastconf
+rm $chunk