title: Relocation R_X86_64_32S against '_Py_NotImplementedStruct' can not be used when making a shared object; recompile with -fPIC
body: <p>I'm trying to install the <code>dlib</code> Python library. On some systems (macOS, stock Ubuntu 14.04) <code>pip install dlib</code> works fine, but in the Ubuntu 14.x that's part of our CircleCI environment it fails with the following error.</p>
  
  <pre><code>Linking CXX shared library dlib.so
     /usr/bin/ld: /opt/circleci/python/2.7.11/lib/libpython2.7.a(abstract.o): relocation R_X86_64_32S against '_Py_NotImplementedStruct' can not be used when making a shared object; recompile with -fPIC
     error: cmake build failed!
  </code></pre>
  
  <p>What could be wrong?</p>