Update for pyenv environment creation on OSX

[bstellato]

I have tried the pyenv environment setup option in #122 but it did not work for me. I was not able to generate the shared library and PyCall was giving the error

ImportError: No module named site

Instead, the following command worked

env PYTHON_CONFIGURE_OPTS="--enable-shared" pyenv install 3.6.5

The difference is to use --enable-shared instead of --enable-framework. This is also described here.

[maximerischard]

I also needed the --enable-shared option on Ubuntu. Otherwise I was getting a Couldn't find libpython; check your PYTHON environment variable. error.

Note that the syntax can be simplified to CONFIGURE_OPTS=--enable-shared pyenv install -f 3.6.5.

[cmcbride]

I am not sure if I should raise a different issue, but using the --enable-shared did resolve my problem so I'm just commenting here for now.

In short, not having the shared library on the python executable installed from pyenv somehow got PyCall to generate an inconsistent deps.jl (it found my 3.8.7 python, but tried to set the libpython to a 2.7 version)

[nibbler deps]% pwd
/Users/cmcbride/.julia/packages/PyCall/tqyST/deps
[nibbler deps]% which python
/Users/cmcbride/.pyenv/shims/python
[nibbler deps]% python --version
Python 3.8.7
[nibbler deps]% python find_libpython.py
/Users/cmcbride/.pyenv/versions/3.8.7/lib/python3.8/config-3.8-darwin/libpython3.8.a%
[nibbler deps]% /usr/local/bin/python find_libpython.py
/usr/local/Cellar/python@2/2.7.17_1/Frameworks/Python.framework/Versions/2.7/Python%
[nibbler deps]% cat deps.jl
const python = "/Users/cmcbride/.pyenv/versions/3.8.7/bin/python"
const libpython = "/System/Library/Frameworks/Python.framework/Versions/2.7/Python"
const pyprogramname = "/Users/cmcbride/.pyenv/versions/3.8.7/bin/python"
const pyversion_build = v"3.8.7"
const PYTHONHOME = "/Users/cmcbride/.pyenv/versions/3.8.7:/Users/cmcbride/.pyenv/versions/3.8.7"
"True if we are using the Python distribution in the Conda package."
const conda = false