Below are my build instructions for GnuPG 2.2.9, released on July 12th, 2018. These instructions are built for a headless Centos 7 LTS server (specificaly the openshift/base-centos7 docker image).
You use the below install script to install GnuPG 2.2.x by running the following commands:
# if you are root in a docker image:
curl -OL "https://gist.githubusercontent.com/simbo1905/ba3e8af9a45435db6093aea35c6150e8/raw/83561e214e36f6556fd6b1ec0a384cf28cb2debf/install-gnupg22.sh" && bash ./install-gnupg22.sh
# else if you need to sudo to do the installs: