Mark libdemangle as vendor_available

The lib is used by libc_malloc_debug_backtrace which is
vendor_available. libc_malloc_debug_backtrace is marked as such because
it is again used by libmemunreachable which is vendor_available.

Bug: 33241851
Test: BOARD_VNDK_VERSION=current m -j libmemunreachable.vendor
Change-Id: I978f8e34d354e4fe03a3c19dd0dbc6899f26a793
1 file changed