* hpx5: Convert to AutotoolsPackage, several updates
- convert to AutotoolsPackage
- add several variants
- add several dependencies
- add new version 4.0.0
- don’t set compiler flags explicitly
* hpx5: Don’t import os
* hpx5: Clean up configure arguments
* hpx5: Correct libffi configure declaration
Also add new variant “+instrumentation”.
* hpx5: Correct CUDA, MPI, OpenCL configuration
* hpx5: Use built-in libffi
Spack’s libffi installs its headers in a strange place, and hpx5 can’t pick them up.
