#1 Define variables for architecture type

[Stefano Borini]

When a package runs, the variable PACKAGE_ROOT_DIR is set to the root of the package.
Additional variables should be defined :
- CN_RUN_ARCH : should be defined containing the architecture of the invoked Executable entry (eg: Linux-i686 if an executable is found, or noarch if the noarch executable is run)
- CN_ENTRY_POINT : contains the invoked entry point