exec_group broken on Windows (0930)

exec_group/3 raises system interface error in cases where exec works:

system interface error: Invalid argument in exec_group('f:\\rotds\\rotd-2001-04-30\\i386_nt\\install\\lib\\i386_nt\\eclipse -e "compile(t_sockets),socket_client(client,southfields / 3945),close(client)"', [null, null, null], _g)