Speed up build times

[ronawho]

We build hwloc and qthreads from source and "install" them under the Chapel source tree. qthreads and hwloc build pretty quickly, but they do spend some time building/installing things that we don't really care about. Here's a couple things I've noticed:

hwloc has an embedded mode. That builds significantly faster so it'd be nice if qthreads were able to use an embedded hwloc.

On the qthreads side of things, it'd be nice if there was a way to disable building/installing the documentation/man pages.

Both of these are pretty low priority for us since it's just build time, but it might be an easy thing to do on a rainy day.

[ronawho]

Still of interest to us as slow / rainy-day work, but still low priority.