set GLVertexAttrib.buf_type when loading a GLMesh

src/shader.cpp

@@ -273,6 +273,8 @@ loadGLMesh(const Mesh& m,
 	for (u32 i = 0; i < num_mappings; i++) {
 		GLBuffer& buf = glm.vertex_attrib_buffers[i];
 		GLVertexAttrib* attrib = mappings[i].attrib;
+		// FIXME: does it make sense to set 'buf_type' in a separate function?
+		attrib->buf_type = mappings[i].buf_type;
 		u32 type_size = getGLTypeSize(attrib->data_type);
 		assert(type_size > 0);