Operating system: Windows 10 64bit
Graphics card: Geforce 1080 ti + Geforce GTX 980
Broken: 2.80, 155c62b070a9, master, 2019-06-26
Short description of error
Baking a texture lightmap on a model which uses a shader with SSS now outputs a corrupted texture.
Exact steps for others to reproduce the error
Open the attached file "Building_Lightbake_test_2_79.blend" in Blender 2.79, select the model and and press "Bake" from the render panel. When baking has completed (Samples are set very low so should only take a few seconds) you'll see a lightmap in the image editor (called Lightbake) and switching the 3d to "Texture" view mode and ticking "Shadless" will show you the baked result looking as expected.
Follow the same procedure in 2.8 using the attached file "Building_Lightbake_test_2_8.blend" but set the viewport to "Solid" mode with the display set to "Flat" & "Texture" to see the baked result. You'll see the baked texture is badly corrupted and mostly black, the material and lighting settings are the same across versions (2.79/2.8)
It seems as though the issue is related to the Sub surface scattering, turning this off in the 2.8 version removes the corruption. However this isn't a fix as the result is not the required look that 2.79 was able to achieve.