message: Fix MissingRequiredAttributes backend test with Metal
diff: @@ -44,6 +44,12 @@ TrianglePrimitive::TrianglePrimitive(filament::backend::DriverApi& driverApi,
  .flags = 0
  }
  };
  +
  + // Backends do not (and should not) know the semantics of each vertex attribute, but they
  + // need to know whether the vertex shader consumes them as integers or as floats.
  + // NOTE: This flag needs to be set regardless of whether the attribute is actually declared.
  + attributes[BONE_INDICES].flags |= Attribute::FLAG_INTEGER_TARGET;
  +
  AttributeBitset enabledAttributes;
  enabledAttributes.set(VertexAttribute::POSITION);
  