scripts/functions: Use stat correctly on non-GNU (BSD/Darwin) systems.

Call to get the directory mode depending on $CT_SYS_OS

yann.morin.1998@anciens.enib.fr:
CT_SYS_OS has changed on Linuxsystem, it only gets the kernel name "Linux",
and not the system name, 'GNU/'.

 reporter_name="Bart vd. Meulen"

 reporter_url=""

 reporter_comment="Sample for building a canadian cross-compiler"