How to reproduce:
1. Open a new project
2. Extract the "MudBun.zip" file into the created project's Assets folder
3. Select the "MarchingCubes" Asset in the Project window (Assets/Resources/Compute)
4. Press "Show compiled code" in the Inspector window
5. Observe the code in the External Script Editor
6. Go back to the Editor
7. Observe the Console log

Expected result: Compiled code is shown in the External Script Editor (step 5) and no errors are shown in the Console log (step 7)
Actual result: "Failed to compile compute shader." is shown in the External Script Editor (step 5). "Shader error in 'MarchingCubes': 'FOR_EACH_BRUSH': Too few arguments to a macro call. at kernel generate_flat_marching_cubes_mesh at BrushMaskFuncs.cginc(116)" error message in shown in the Console log (step 7)

Reproducible with: 2020.2.0a13, 2020.2.0b3
Not reproducible with: 2019.4.11f1, 2020.1.6f1, 2020.2.0a12
Could not test with: 2018.4.27f1 (Multiple errors due to unsupported features, such as SceneVisibilityManager, Graphics.DrawProceduralIndirect)

Beta Forum Thread:
https://forum.unity.com/threads/shader-macro-with-multi-line-arguments-fails-to-compile.974061/