Klever

At the moment exit codes of wrapped build commands are totally ignored. But this implicitly breaks the Linux kernel build since it assumes that if, say, GCC doesn't support some option it fails and this option isn't invoked during further build.

Likely this issue has many bad consequences, in particular, we will be able to avoid ugly workarounds adapting Linux kernel build for our old-school Aspectator, maybe some modules and the whole Linux kernel will be successfully built without any strange failures.

Thanks to Ilja Schepetkov that helped to identify this issue!