dotnetenv needs DOTNET_ROOT to detect .NET on Linux, macOS

This is a solution to an undocumented issue:

dotnetenv() documentation (or anywhere else on mathworks.com) doesn't mention that environment variable DOTNET_ROOT is vital for Matlab to detect the .NET installation, particularly on non-Windows platforms newly supported for .NET.

If anyone is having an issue getting Matlab to detect their .NET installation, particularly on macOS or Linux:

from system Terminal: dotnet --info

in Matlab, if getenv("DOTNET_ROOT") isn't set or doesn't match dotnet --info:

setenv("DOTNET_ROOT", <DOTNET_ROOT path from dotnet --info>)

in Matlab: dotnetenv("core", Version=<major version .NET installed>)