Evaluate using `Popen(shell=False, ...)`

[smarr]

Should we avoid using the shell for running commands?

Think this is a major change at the core of ReBench. So, we'd probably need to carefully test this. See https://github.com/smarr/ReBench/pull/248#issuecomment-2269272256

[smarr]

At the moment, we request explicitly the use of a shell here: https://github.com/smarr/ReBench/blob/master/rebench/executor.py#L532

However, we run build commands without shell here: https://github.com/smarr/ReBench/blob/master/rebench/executor.py#L397