Allow multiple parallel kernel builds

[0xricksanchez]

Is your feature request related to a problem? Please describe.
Currently, we allow re-using a built kernel across runs.
However, if we were to hop between kernel version/architectures we're overwriting the at that moment built kernel as the same directory is used.

Describe the solution you'd like
It would be sweet to re-use the kernel_root directory but add subdirectories in the form of , which are defined in the config.ini.
The logic would need to be adjusted to consider these subdirectories properly
Anyhow, this could be a big win especially to debug kernel revisions side by side.

To account for side-by-side builds we need to fix the vm.pid file in the debuggee as well.
Either delete that parameter or make the naming depend on a dynamic runtime feature!