Proc.restore_cwd_and_execve prog args ~env runs prog with args in env.

• prog is the program being run. It should be a filename in the current working directory.

• args is a list of arguments to the program. Unlike in the system call execve, the first argument is not the program name. The first argument is the first argument to the program. The program name is set to prog without the caller needing to.

• env is the environment in which the program is run.

This function is not implemented on Windows