message: [build] make boost-process opt-in
diff: @@ -1198,7 +1198,9 @@ fi
  AX_BOOST_SYSTEM
  AX_BOOST_FILESYSTEM
  AX_BOOST_THREAD
  -AX_BOOST_PROCESS
  +
  +dnl Opt-in to boost-process
  +AS_IF([ test x$with_boost_process != x ], [ AX_BOOST_PROCESS ], [ ax_cv_boost_process=no ] )
  dnl Boost 1.56 through 1.62 allow using std::atomic instead of its own atomic
  dnl counter implementations. In 1.63 and later the std::atomic approach is default.
  