Board not detected if working directory is not the root directory

[jolivepetrus]

If in system.lua or autorun.lua current difectory is changed the environment don't detect the board.

Notes:

The startup procedure of the environment sends a Ctrl-C to the board for stop the execution of the current script and then waits for a "/ >". If the current script changes the working directory, for example, /sd when Ctr-C is received a "/sd >" is received.

A more sophisticated approach is needed. For example, calling a new proposed function os.version()