Changed minimal version of C++ standard to C++17

[xvitaly]

Changed minimal version of C++ standard to C++14. Google Test since version 1.13.0 requires C++14.

Closes #877.

[veloman-yunkan]

The CI of this PR fails in the same way as #878 (thus the issue was not caused by the + symbol in the branch name). By looking closer it turns out that the checkout step attempts to clone the repository from kiwix rather than from @xvitaly's fork and fails because the branch is only present in the fork. This problem should be present with any PR created against a fork.

Now, looking in .github/workflows/ci.yml I see that the Checkout code step uses actions/checkout@v2 under macos (which works) but a custom command line under linux. I wonder why actions/checkout isn't used in the latter case.

The same issue with CI workflow configuration is present in libzim.

[veloman-yunkan]

@mgautierfr @kelson42 Do you know of any reason why actions/checkout is not used under linux in our CI?

[mgautierfr]

Do you know of any reason why actions/checkout is not used under linux in our CI

There is a small information in the commit message here : openzim/libzim@34aba05f

The thing is that we reuse the dependencies build by kiwix-build and there is some (?) conflict between path and write rights.
I don't remember which one exactly. But if you want to fix that, you are more than welcome 😃

[kelson42]

Actually we will should move straight to C++17.

[xvitaly]

Actually we will should move straight to C++17.

Should I update my PR to c++17?

[kelson42]

@xvitaly As far as I understand from @mgautierfr, we have a few things to sort out before. For the moment I would just wait a bit. We might fix all of that this WE.

[xvitaly]

Updated PR to C++17.

[kelson42]

Closing for the moment as we have external blockers. Might be reopened when they will be fixed.