amazonlinux support

[gaborbernat]

Resolves #1719.

[gaborbernat]

@tzulberti can you validate that this solves your issue?

[tzulberti]

I tested this issue by doing a git clone inside a Docker image:

FROM amazonlinux:1

RUN yum -y install python27 python27-devel python36 python36-devel python27-pip git

#RUN pip-3.6 install --upgrade virtualenv
RUN pip-3.6 install --upgrade 'setuptools>=41'
RUN pip-3.6 install --upgrade wheel
RUN git clone https://github.com/gaborbernat/virtualenv.git && \
    cd virtualenv && \
    git checkout 1719 && \
    pip-3.6 install .

RUN cd /root && virtualenv --python python2.7 /tmp/bar

RUN source /tmp/bar/bin/activate && pip freeze

And it seems to work ok