Build VNDK APEX for VNDK-Lite

For VNDK-Lite devices, which doesn't define BOARD_VNDK_VERSION, VNDK
APEX is built with only VNDK-Sp libraries with core variants.

Bug: 141908078
Bug: 152353068
Bug: 151635128
Test: TH
Change-Id: I0d08d32473368fd158818d4c2c72fc4cfad68ce6