This diffs cleans up the console output from the shell trace, making it
easier to read the teamcity build log (the shell traces are printed to stderr,
generating warnings). It also generates a couple log files which are always
added to the artifacts:

• A clean log which has the same content as the console output for thebuild
• A full log that includes the traces removed from the console output.

Depends on D6735.

Run any CI build plan.
Check the build log is free from the shell traces and that the artifact
archives contains the 2 build log variants at its root.