Remove conditional define when optional dependency leaves a project

[amirebrahimi]

This can likely be fixed by using an AssetPostprocessor or the CompilationPipeline (requires 2017.3 or later).

CCU will still be in memory before the project recompiles and could makes this fix before the compilation, so it doesn't leave the project in a broken state.

[Dorgam]

Hi,

Any updates on this?

I really need to remove the defines if I uninstall a plugin. Any way to achieve that?

Thank you.

[amirebrahimi]

Added with b3523ea