Comment (by Roland Haas):

I think the issue was some AMD clang compiler on Frontier that, while accepting -std=c++17 would only provide filesystem in experimental. On the other hand just testing this right now, I cannot make it fail.

Well, I will see if I can set this ticket to sleep for a bit.

--
Ticket URL: https://bitbucket.org/einsteintoolkit/tickets/issues/2885/test-for-std-filesystem-availability-in