Much as we have devtoolset-6 in dist-git, we'll need devtoolset-7, also. This is a tracker bug for the addition.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHEA-2017:3008