Stop using weak symbols in libvndksupport.

These weak symbols are no longer necessary because we no longer
need to statically link libvndksupport.

Furthermore, these symbols are not really optional when libvndksupport is
dynamically linked. When the library is linked with --as-needed the linker
may drop the reference to libdl_android.so, which leads to a failure to boot.

Bug: 146456667
Change-Id: I4d2290d8d0206e0d89665d4d872a7c53b3e1531b