title: Bazel cross compile of tensorflow for ARM fails
body: <p>I am trying to build tensorflow to run on a Zynq, specifically, the Z7020.  I have petalinux running on the board, and python 3.4.9.  When trying to build tensorflow following the instructions found here:[<a href="https://www.tensorflow.org/install/install_raspbian#cross-compiling_from_sources]" rel="nofollow noreferrer">https://www.tensorflow.org/install/install_raspbian#cross-compiling_from_sources]</a>
  Note that both petalinux and raspbian are both Debian derivatives and the Z7020 has the same CortexA9 cores as the raspberry-pi 0 and 1 series boards.</p>
  
  <p>I am trying to build on an Ubuntu 16.04 host.  The command I am using to build is:</p>
  
  <pre><code>sudo CI_DOCKER_EXTRA_PARAMS="-e CI_BUILD_PYTHON=python3 -e CROSSTOOL_PYTHON_INCLUDE=/home/rklein/Python-3.4.9/Include" tensorflow/tools/ci_build/ci_build.sh PI-PYTHON3 tensorflow/tools/ci_build/pi/build_raspberry_pi.sh PI_ONE
  </code></pre>
  
  <p>Bazel churns for about 2 hours and comes back with the following error message:</p>
  
  <pre><code>    /home/rklein/tensorflow/bazel-ci_build-cache/.cache/bazel/_bazel_root/eab0--lots of hex digits--85e8/external/arm_compiler/bin/arm-linux-gnueablhf-gcc --lots of options
  
      In file included from /usr/include/python2.7/Python.h:8:0, from ./tensorflow/python/lib/core/bfloat16.h:19, 
                       from tensorflow/python/lib/core/bfloat16.h:18:
                       from /usr/include/python2.7/pyconfig.h:13:54: 
      fatal error: arm-linux-gnueabihf/python2.7/pyconfig.h: No such file or directory
      #include &lt;arm-linux-gnueabihf/python2.7/pyconfig.h&gt;
                                                         ^
      compilation terminated.
  </code></pre>
  
  <p>What settings are needed to tell Bazel to use python3?  Note that there is no /usr/include/python2.7 directory on the host machine, so I suspect that Basel is doing some voodoo behind the scenes.  The command</p>
  
  <pre><code>find ~ -name python2.7
  </code></pre>
  
  <p>comes up empty.</p>
  
  <p>I have tried to read up as much as I can on Bazel, but the documentation seems pretty lean - any good references would be appreciated.</p>