write a foot to execute the subprojects of the build subdirectory respectively.
if I use the following script to clear the builds of all subprojects

-sharp!/bin/sh

dirs=`find . -maxdepth 1 -type d`

for fname in $dirs
do
     echo $fname
     if [ -e $fname/pom.xml ]
     then
      mvn clean -f $fname/pom.xml
     fi
done