libsync is used both by platform (e.g. libui.so) and by same-process
HALs (e.g. android.hardware.graphics.mapper@2.0-impl.so). Therefore it
is eligible for either VNDK-SP or LL-NDK. Among the two choices, LL-NDK
was selected because it is already an NDK and is just a thin wrapper
around a few kernel ioctls.
However, since libui (which is a vendor_available:true library) is using
more symbols that are not available to NDK clients, the extra symbols
are exposed as # vndk tag so that they are only available to VNDK
clients, but not to NDK clients.
Bug: 63866913
Test: BOARD_VNDK_VERSION=current m -j successful (2017 pixel)
Test: the built image is bootable
Change-Id: I60f883c049bd9b4562e6ce34d34ead47ba28af5f
058e0919f6