add config options for rfsimulator, set a common lib for l1sim and rfsimulator, avoid simulation sources to be added twice in some execs (tau.c)

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

try to fix build failure due to increased number of build files on some build commands (=> more log files)

For whatever reason most of the files had their permission
changed from 644 to 755, which is not wanted.