Virtual Masters not recognized on build

https://github.com/Afrotype/danfobase/issues/2

https://github.com/Afrotype/danfobase/actions/runs/6949071877

https://github.com/googlefonts/glyphsLib/issues/859#issuecomment-1821172843

_Relevant conversations above_

Expected behavior: The shape element _part.cut which is part of the H as scallops on the side should be able to be controlled by the ELSH axis

Observed behavior: The builder runs and produces a static font but doesn't recognize the virtual master setup.