Adding a mechanism to conditionally exclude some header library
dependencies when a lib is built for vendors.
Without this, some libraries cannot be earily marked as vendor_available
if they are depending on header libs can shouldn't be marked as
vendor_available.
By using exclude_header_libs with exclude_srcs (or __ANDROID_VNDK__
macro), we can eliminate the unnecessary dependency for vendors.
Bug: 112338314
Test: build
Change-Id: If12dceb6045099fe828fe33af2ac4428f88499a2
8dbc653dff