To install latest git on centos 7, use an RPM. building from source without an rpm will result in a dependency breaking it later (eg installing gitlab) https://medium.com/better-programming/install-git-v2-on-centos-7-49448deede19
To configure gitlab runner, ensure these lines are present.
concurrent = 2
check_interval = 0
[session_server]
session_timeout = 1800