tools: Make sethost.sh can be invoke from any directory

tools/configure.sh

@@ -282,6 +282,4 @@ fi
 # The saved defconfig files are all in compressed format and must be
 # reconstitued before they can be used.
 
-cd ${TOPDIR} || { echo "Failed to cd to ${TOPDIR}"; exit 10; }
-
-./tools/sethost.sh $debug $host
+${TOPDIR}/tools/sethost.sh $debug $host

tools/sethost.sh

@@ -125,6 +125,9 @@ if [ ! -z "$1" ]; then
   showusage
 fi
 
+WD=`test -d ${0%/*} && cd ${0%/*}; pwd`
+cd $WD
+
 if [ -x sethost.sh ]; then
   nuttx=$PWD/..
 else