Cannot use pyROOT from a conda python installation

No matter how hard I try, I cannot import ROOT from a conda installation of python.
Given the widespread use of conda as a python package manager, I think ROOT should have a working formula that allow users to use conda and pyROOT together.

Configuring CMake with
cmake -DPYTHON_EXECUTABLE=/home/eguiraud/Tools/miniconda2/bin/python path/to/root
and then building, this is what I get at python prompt:

$ source $ROOTSYS/bin/thisroot.sh

$ python

>>> import ROOT

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

  File "/home/eguiraud/ROOT/root_build/lib/ROOT.py", line 24, in <module>

    import cppyy

  File "/home/eguiraud/ROOT/root_build/lib/cppyy.py", line 61, in <module>

    import libPyROOT as _backend

ImportError: /home/eguiraud/Tools/miniconda2/lib/libstdc++.so.6: version `GLIBCXX_3.4.21' not found (required by /home/eguiraud/ROOT/root_build/lib/libPyROOT.so)

It was suggested I should not source thisroot.sh (which is weird since most ROOT users just do it in their bashrc or anyway when they setup their working environment) and just export PYTHONPATH=$ROOTSYS/lib, but this yields similar results.