contrib/packaging/docker/rhel7

setup: try a non-pure version of the local Mercurial if the pure fails

Things like `zstd` can make the pure version fails.

FROM centos:centos7

RUN groupadd -g %GID% build && \
    useradd -u %UID% -g %GID% -s /bin/bash -d /build -m build

RUN yum install -y epel-release
RUN yum install -y \
	gcc \
	gettext \
	make \
	python3-devel \
	python36-docutils \
	rpm-build \
	tar

# For creating repo meta data
RUN yum install -y createrepo

# For rust extensions
RUN yum install -y cargo