Reconfigure SonarCloud

[abitmore]

We were using SonarCloud with Travis CI. Since we're moving away from Travis CI, if we still want to use SonarCloud, we need to find a way to make it work again.

Related: #836 #2312

[abitmore]

I found this: https://github.com/SonarSource/sonarcloud-github-action which seems to be for Github Actions, but according to the README file:

Do not use this GitHub action if you are in the following situations

• You want to analyze C/C++ code: rely on our Travis-CI extension and look at our sample C/C++ project

It seems we can't use it. And we are not going to Travis-CI.

In a forum thread https://community.sonarsource.com/t/when-will-sonarcloud-c-c-analysis-support-github-actions/35994 there is more info:

you can analyze C/C++ code on GitHub actions, the only condition is that you don’t use predefined SonarCloud actions. What you have to do is to setup the analysis as part of the build action, the analysis must run in the same OS layer/environment of the build.

[abitmore]

This seems to be what we're looking for: https://github.com/marketplace/actions/sonar-scanner .

[abitmore]

Done via #2367.