gltfpack: Don't optimize out translation tracks under scale=0 nodes
gltfpack: Don't optimize out translation tracks under scale=0 nodes

When a node has a scale of 0 it's likely that it has a scale animation
that makes the object visible; in this case, we're going to ignore the
scale for the purpose of translation estimation to avoid folding of
translation tracks.

zeux/meshoptimizer,zeux/meshoptimizer,zeux/meshoptimizer