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/'.

 #!/bin/sh

 SKIP_ME="### CT_NG SKIP ME ###"

 skip_me=$(($(cat "${0}" |@@grep@@ --binary-files=text -o -b -E "^${SKIP_ME}$" |cut -d : -f 1)+${#SKIP_ME}+1))

 dd if="${0}" bs=${skip_me} skip=1 2>/dev/null |bzcat

 exit 0

 ### CT_NG SKIP ME ###