Issue: During VSTS agent build, you encounter errors similar to this one. Most likely during builds involving Fody:

Error: Fody: An unhandled exception occurred:
Out of memory

Cause: This appears to be a bug related with Mono/Cecil/Fody

Solution: The current solution is to change Visual Studio for Mac or Xamarin's preference > .NET Runtimes default to "Mono 4.8.0." Please contact our support so we can carry out the setting change for you.