New Windows compiler error introduced by Mantaflow change

I was asked to post this here as well. The details are also available at https://developer.blender.org/T76276.

Basically, this commit (https://developer.blender.org/rB21485e94aac1bc01d032f666ebc54c6008f4d303) ended up adding more if/else clauses to the MANTA_main.cpp file which pushed it past 128 clauses. As a result the MSBuild compiler has a fatal error as this exceeds its limit of 128 nested clauses. The end result is Blender can no longer compile on Windows past this commit.

On a larger note, that code is really quite messy and could use a refactor to clean it up versus just doing a bunch of nested string comparisons - even a switch() would be better I would think. That said, I’m no C++ architect and don’t want to overstep my bounds.