tile: thin archives fix linking

The VDSO symbols can't be linked into built-in.o when building with
thin archives, so change this to linking a new object file that is
included into the built-in.o.

Cc: Chris Metcalf <cmetcalf@mellanox.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>