Spack Build Issues

with clang on sierra, python builds w/o ctypes support: This causes py-setuptools to fail.

==> '/p/gpfs1/cyrush/2018.11.ascent.xlc/ascent/uberenv_libs/spack/opt/spack/linux-rhel7-ppc64le/clang-coral/python-2.7.15-nc4tjupjudvrdyck4mj53i33p3q4tk5u/bin/python2.7' '-s' 'setup.py' '--no-user-cfg' 'build'
Traceback (most recent call last):
  File "setup.py", line 11, in <module>
    import setuptools
  File "/tmp/cyrush/spack-stage/spack-stage-3MVWpq/setuptools-40.2.0/setuptools/__init__.py", line 16, in <module>
    from setuptools.dist import Distribution, Feature
  File "/tmp/cyrush/spack-stage/spack-stage-3MVWpq/setuptools-40.2.0/setuptools/dist.py", line 25, in <module>
    from setuptools import windows_support
  File "/tmp/cyrush/spack-stage/spack-stage-3MVWpq/setuptools-40.2.0/setuptools/windows_support.py", line 2, in <module>
    import ctypes
  File "/p/gpfs1/cyrush/2018.11.ascent.xlc/ascent/uberenv_libs/spack/opt/spack/linux-rhel7-ppc64le/clang-coral/python-2.7.15-nc4tjupjudvrdyck4mj53i33p3q4tk5u/lib/python2.7/ctypes/__init__.py", line 7, in <module>
    from _ctypes import Union, Structure, Array
ImportError: No module named _ctypes

On Cori, python+shared ends up with a python polluted by the system python:

import sys;from distutils.sysconfig import get_python_inc;sys.stdout.write(get_python_inc())
/usr/include/python2.7