-net-std=/dotnet how to set this up to avoid error?

I’m learning to compile dll for different targets.
Its explained on this page .NET version and external libraries - Haxe - The Cross-platform Toolkit

This is the command:
-D net-target=micro -D net-ver=35 -net-std=/dotnet

I get this error:
Error: No .NET std lib directory with the pattern ‘micro -d net-ver=35 -net-std=/dotnet-20’ was found in the -net-std search path. Try updating the hxcs lib to the latest version, or specifying another -net-std path.

I’m guessing its something to do with the /dotnet folder which I have no idea what its suppose to be in it? I’m on a mac, there is a /dotnet folder at this location:


inside this folder I have folders such as sdk, host, share…

I try setting -net-std=/usr/local/share/dotnet but its the same error.

How do I set up my environment so I can target other .NET versions?