Udon ignore compile constant

[CorneliusCornbread]

Compile time constant (ex UDON_COMPILE) that is false only when udon compiles the script/ignores everything inside the #if compile check.

I'm trying to make use of some MyBox attributes to make sorting things in the inspector easier and being able to use them while Udon doesn't throw a fit would be nice.

[MerlinVR]

This is currently provided by the COMPILER_UDONSHARP constant which is only true when code is being compiled by UdonSharp.