[MacPorts] #54149: gcc6 fails to compile because "configure: error: cannot compute sizeof (long long)"

[Ryan Schmidt]

>> I have been updating gcc7 snapshots weekly and stopped recently when I realized they were preparing for the first release. I did not know they had now done so. I will update the ports once a snapshot of gcc8 is available (probably already is), since gcc6, gcc7 and gcc8 will need to be updated at the same time to move the libgcc subports around. 
> 
> Great, thanks. 7.1 has been released on May 2nd so it's still really fresh. Updating should just be a question of pointing the portfile to the release tarball, right?

It's a matter of doing the equivalent of this, with updated versions:

https://github.com/macports/macports-ports/commit/c4ddd1af302d5be105cbd58d2cb5dce89e892858

I will work on it later.