title: make -jXXX : how can I get XXX
body: <p>I have a parallel test suite (perl prove -j XXX).   If a user types make -j 8 all, I'd like the test suite to be run with the same parameter: prove -j XXX t.   If not, then I'd like it to be run single-threaded.   Since I know the test suite is top level and depends on all of the binary targets, I'd like to, very simply, pass-through the user's specified parallel argument.</p>
  
  <p>Is there something in gnu make that allows for getting the command-line arguments used to run make?  Or will the user have to do something like: make -j 8 PLL=8 all.</p>