'Indirect Lighting' MaterialXView option broken on macOS

[pablode]

It does not seem to do anything, while on Windows it works:

Screen.Recording.2026-04-03.at.15.00.28.mov

[jstone-lucasfilm]

Good catch, @pablode, and my initial guess is that we're referencing a hardcoded uniform name that doesn't match the behavior of the MSL shader generator.