`batch_for_shader` is an utility function that creates the correct
vertex buffer based on the given shader. In the shader interface
the `attr_types_` contains the GPUType for each location in the
vertex buffer.
When using Metal, the `attr_types_` was never updated, resulting
in using incorrect or non-existing data types. This patch fixes
this by updating the `attr_types_` when building the shader
interface.
Reviewed By: fclem
Differential Revision: https://developer.blender.org/D17042
7f81d18ffe