Issue: You are facing an error in VSTS agent build: MsBuild.exe does not exist at '/Library/Frameworks/Mono.framework/Versions/4.6.1/lib/mono/4.5/msbuild.exe'.
Cause: This is a known NuGet bug ( https://github.com/NuGet/Home/issues/3085) and the fix will be in 3.5-rtm release
Solution: Please reference the following screenshot and use the custom NuGet.exe located at /Library/Frameworks/Mono.framework/Versions/4.6.1/lib/mono/nuget/NuGet.exe
(Courtesy of Madhuri from Microsoft and Joe from Xamarin. Source: https://github.com/Microsoft/vsts-tasks/issues/2828)
Please contact our support if you have more questions.