vndk-def: Add NDKLibDict.classify().

This commit adds NDKLibDict.classify() so that we can get the type of
NDK libraries (e.g. LL-NDK, SP-NDK, or HL-NDK.)

Test: ./tests/run.py
Change-Id: I332af0d50a403a719c4b4bb586c6cb20f925bcc4
2 files changed