"Link Assemblies" task failed unexpectedly issue while App build in Release Mode Xamarin Android

I was able to resolve the issue in by changing the Target Android Version and setting the Java Max Heap Size in the following manner.

1. Right click MyApp.Droid
2. Properties > Android Options > Advanced (tab)
3. Set 'Java Max Heap Size' to 1024m

Try this configuration for Debug mode

I got this too after upgrading to Xamarin Forms. You need to make sure your Target Framework is the last version.