softmmu/datadir.c had its own implementation to find files in the
build tree, but now bundle mechanism provides the unified
implementation which works for datadir and the other files.

Signed-off-by: Akihiko Odaki <akihiko.odaki@gmail.com>
Message-Id: <20220624145039.49929-4-akihiko.odaki@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>