title: create directory when needed in maven
body: <p>I am using maven-exec-plugin to generate java sources of Thrift. It invokes the external Thrift compiler and using -o to specify the output directory, "target/generated-sources/thrift". </p>
  
  <p>The problem is neither maven-exec-plugin nor Thrift compiler automatically create the output directory, I have to manually create it.
  Is there a decent/portable way use create missing directories when needed? I don't want to define a mkdir command in the pom.xml, since my project need to be system independent.</p>