Created attachment 218773 [details]
Without -std=c++17 devel/abseil causes dependent port failure, for example math/or-tools (version 8.0) fails to compile. See the suggestion of or-tools' upstream maintainer that abseil needs c++17 here: https://github.com/google/or-tools/issues/2196#issuecomment-707762185
Comment on attachment 218773 [details]
I take back the original patch.
It looks like this port should be flavorized based on the C++ standard used in it, since users seem to be sensitive to this.
I suggested the upstream to uniquify paths based on CMAKE_CXX_STANDARD: https://github.com/abseil/abseil-cpp/issues/820
Otherwise it wouldn't be possible to update math/or-tools to 8.0.