Request: Add build compiling with `C++20` to GitHub actions.

[phcerdan]

CDash has builds with C++17 enabled, but they are not triggered when github builds opened PR's.

It would be great to have at least one build (gcc or clang) in github wih C++17.

[dzenanz]

In #2900, a new build was added: LinuxLegacyRemoved. This is being run in our itkrobot.linux Azure account (there are different accounts due to CI execution time limit). A similar thing could be done for MacOS platform, but instead of disabling legacy, enable C++17. Just copy-paste the existing job, modify its name and add C++17 compiler flags where appropriate. The effort will mostly consist of testing, making sure that everything works as intended.

[dzenanz]

@devbanu you need to comment here before I can assign this to you.

[devbanu]

OK. I am trying to fix this issue.

[devbanu]

@dzenanz @phcerdan

Since this issue was created, it seems that the C++17 has been enabled for the whole ITK project in #2563.

But this functionality is still interesting, e.g. for C++20, and so on, so that for a PR one can test with newer standards.

[dzenanz]

Great observation! Can you instead modify one of the builds to use C++20?