title: speed up autoconf/configure of large project
body: <p>I have a large autoconf/automake project, broken into components using AC_CONFIG_SUBDIRS.  Is there any way to make autoconf/configure run faster?  Perhaps doing subdirs in parallel, or caching reusable findings? </p>
  
  <p>I could easily write a build script that would build components in parallel, but would prefer to not add a secondary point of build structure maintainance. </p>