Fail the CI if certain warnings are found

[Xazax-hun]

Is your feature request related to a problem? Please describe.
This feature request was mentioned on cfe-dev mailing list and the use-case is already supported by scan-build: http://lists.llvm.org/pipermail/cfe-dev/2019-June/062495.html

Describe the solution you'd like
It should be possible to treat certain checkers or compiler warnings as compilation errors.

Describe alternatives you've considered
Alternatively one could use parse to get the list of warnings from the run and process the result with a script. This is, however, not user friendly at all. We should not require the users to maintain additional scripts for such a simple task.

[LebedevRI]

the use-case is already supported by scan-build

I'm also missing scan-build's

 --status-bugs

   By default, the exit status of scan-build is the same as the executed build
   command. Specifying this option causes the exit status of scan-build to be 1
   if it found potential bugs and the exit status of the build itself otherwise.

Presumably it would be a flag to analyze sub-command.

[LebedevRI]

@bruntib Looks like this can be closed now?
Hurray!