Support ":vndk" to use vndk libs from vendor apex

Vendor APEX can be configured to use VNDK libs from the outside of the
apex. The dependency to external VNDK is marked in apex_manifest's
"requireNativeLibs" field as ":vndk", which is a pseudo name of VNDK
libs.

Bug: 159576928
Test: ./rundiff.sh
Change-Id: I6dd85270354d085877014c39088969c62314f614
9 files changed