ld.config: Permit legacy /system/vendor paths

Because /vendor is a symlink to /system/vendor on devices without a
dedicated /vendor partition, /system/vendor/lib/* needs to be added to
the permitted paths whereever /vendor/lib/* is permitted.

Reasoning:
Legacy devices are forced to use ld.config.legacy.txt, which is very
permissive. We can prolong support for them and enable them to use the
VNDK if we extend the search paths to include the resolved symlink dirs.

Change-Id: I6b3bb7b86ed82395345a16bdc857353b1b15c704