title: How to deal with "clang: error: unsupported option '-fopenmp'" on travis?
body: <p>I am currently trying to deploy a project using <code>openmp</code>. I have the flag <code>'-fopenmp'</code> on Travis.</p>
  
  <p>How could I fix that ?</p>
  
  <p>In local I just <code>brew install libopenmp</code> which solved the issue. But not on Travis, what are the options ?</p>
  
  <p>Using cython I got the following ".travis.yml"</p>
  
  <pre><code>os: linux
  
  dist: xenial
  
  language: python
  
  python:
    - "3.7"
  
  cache: pip
  
  addons:
    apt:
      packages:
        - patchelf
  
  matrix:
    include:
    - os: osx
      # No version of Python is available via virtualenv on OS X workers, see https://github.com/travis-ci/travis-ci/issues/2312
      language: generic
      env: TOXENV=py37
  
    fast_finish: true
  
  before_install:
    brew install libomp
  
  install:
    - pip install --upgrade "pip &lt; 19.1" -r CI/requirements.txt
    - python setup.py develop
  
  script:
    - pytest
  </code></pre>
  
  <p>Travis fails while executing :</p>
  
  <blockquote>
    <p>clang -fno-strict-aliasing -fno-common -dynamic -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -I/usr/local/include -I/usr/local/opt/openssl@1.1/include -I/usr/local/opt/sqlite/include -I/usr/local/Cellar/python@2/2.7.17/Frameworks/Python.framework/Versions/2.7/include/python2.7 -c cpt/alphabet.c -o build/temp.macosx-10.13-x86_64-2.7/cpt/alphabet.o -fopenmp</p>
  </blockquote>
  
  <p>While in local it compiles with <code>python 3.7</code>, how could I fix that aswell ?</p>