contrib/docker/centos7

test-add.t: fix output difference between Windows and OS X (issue4603)

FROM centos:centos7
RUN yum install -y gcc
RUN yum install -y python-devel python-docutils
RUN yum install -y make
RUN yum install -y rpm-build
RUN yum install -y gettext
RUN yum install -y tar
# For creating repo meta data
RUN yum install -y createrepo