Compiling on Mac

[Ian DesJardin]

Hi Y'all,

I've been trying to get this to compile natively on a Mac (github hash a0789aa5dd79cb481713a8ebdc4f69b0fa20fb97 version on master). Here's some of the issues and partial fixes that I've run into:

- 'gcc' command defaults to using clang on Mac because Apply tries to force clang on everyone. 

Fix: Replaced instances of g++ and gcc with gcc-8 and g++-8 to force it to use my Homebrew version of gcc/g++ that's installed

[Ian DesJardin]

- beast was not linking with Python

Fix: added -lpython2.7 flag to Makefile

- Missing python packages

Fix: brew install opencv --python

- Astropy install instructions didn't work

Fix: pip install astropy --no-deps (from http://docs.astropy.org/en/stable/install.html)

- Different python version used to compile than in runtime

Fix: Pending

 

[Ian DesJardin]

- Different python version used to compile than in runtime

Compiling with gcc and running with python installed via Homebrew (https://brew.sh/) is easiest. In unit_tests.sh the python executable is hardcoded to /usr/bin/python. Changed to /usr/local/bin/python (Homebrew installation) and all appears to work. 

This probably brings up the point that python executable path shouldn't be hardcoded. Andrew - what's your thoughts on how we should handle being flexible about this? (I'd be happy to code up the solution)