Face orientation is not taken into account when baking a one-sided geometry with a transparent texture. Shadows are always baked onto lightmap static geometry regardless of its orientation. This is not expected unless it is specified as double-sided by the user.

Steps for reproduction:
1) Download the project `shadows_test.zip`
2) Open the scene `transparent_1_sided`
3) Bake the scene
4) Observe the outcome

Notes:
- Not a regression, this feature was designed like this