[build]: Fix build on Mac OS X, both intel and Arm architectures.

[appetrosyan]

This is a placeholder issue for fixing PolyChord on Mac OS; while this might not be a high priority yet, not being able to test out theories on a mac environ is a problem.

This is going to involve fixing a few flags and un-resolving a few symlinks that lie. Namely the linker on Mac OS is not GNU LD, which causes the issue with the compiler flag ld: unknown options: -commons.

There are other issues which make the installation sub-optimal, so the PR shall be accompanied by a thorough modification of the README to reflect those changes.

[appetrosyan]

After a bit of digging, I think it can be simply disabled on Mac OS X. It would cause a performance degradation, but that's inevitable on a portable device.

[appetrosyan]

Actually, this is no longer necessary for FORTRAN programs

HDFGroup/hdf5#3571

I'll open a PR to fix

[appetrosyan]

#104 Has a true fix. It should be reflected in the Readme.