[build] Ensure build ID is deterministic

[build] Ensure build ID is deterministic

Commit 040cdd0 ("[linux] Add a prefix to all symbols to avoid future
name collisions") unintentionally reintroduced an element of
non-determinism into the build ID, by omitting the -D option when
manipulating the blib.a archive.

Fix by adding the -D option to restore determinism.

Reworded-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>