package.bbclass: make do_split_packages handle non-existent root directories
This function has different behaviour if the split directory doesn't exist
depending on the recursive argument: non-recursive uses os.listdirs which throws
an exception, recursive uses os.walk which doesn't.
do_split_packages should silently handle non-existent directories because it's
mainly used for plugin directories, which may end up being empty though changing
the distro configuration (for example, connman without wifi distro feature).
So, add an early exit if the split root doesn't exist.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Saul Wold <sgw@linux.intel.com>
