Update CentOS 7 image to use GCC 8
Update CentOS 7 image to use GCC 8

actor-framework/actor-framework,DavadDi/actor-framework,DavadDi/actor-framework,actor-framework/actor-framework,actor-framework/actor-framework,DavadDi/actor-framework,actor-framework/actor-framework,DavadDi/actor-framework