Repro steps:
* Import attached Bolt 2 graph
* Maybe need to add the class to a gameobject component
* Select "Generated" in the Bolt  "Global runtime mode" menu at the top.
* => Exception.

We probably want to make sure this is supported. 

{code:java}
Unity.Bolt.CodeGenerationException: Failed to generate value output expression. ---> System.NotSupportedException: Material does not support code generation.
at Unity.Bolt.SingleDecoratorProvider`3[TDecorated,TDecorator,TAttribute].GetDecoratorType (System.Type decoratedType) [0x00036] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Core\Editor\Decorators\SingleDecoratorProvider.cs:110
at Unity.Bolt.SingleDecoratorProvider`3[TDecorated,TDecorator,TAttribute].CreateDecorator (TDecorated decorated) [0x00029] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Core\Editor\Decorators\SingleDecoratorProvider.cs:44
at Unity.Bolt.SingleDecoratorProvider`3[TDecorated,TDecorator,TAttribute].GetDecorator (TDecorated decorated) [0x000a7] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Core\Editor\Decorators\SingleDecoratorProvider.cs:293
at Unity.Bolt.SingleDecoratorProvider`3[TDecorated,TDecorator,TAttribute].GetDecorator[T] (TDecorated decorated) [0x00001] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Core\Editor\Decorators\SingleDecoratorProvider.cs:307
at Unity.Bolt.XGeneratorProvider.Generator[TGenerator] (System.Object o, Unity.Bolt.IGeneration generation) [0x00001] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Core\Editor\Generation\GeneratorProvider.cs:24
at Unity.Bolt.BoltGenerationUtility.GenerateLiteral (System.Object o, Unity.Bolt.IGeneration generation) [0x00013] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Core\Editor\Generation\BoltGenerationUtility.cs:43
at Unity.Bolt.LiteralUnitGenerator.GenerateOutputExpression (Unity.Bolt.MethodGeneration method) [0x00001] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Flow\Editor\Units\LiteralUnitGenerator.cs:21
at Unity.Bolt.UnitGenerator`1[TUnit].GenerateValueOutputExpression (Unity.Bolt.MethodGeneration method, Unity.Bolt.ValueOutput valueOutput) [0x00033] in C:\Users\laurent.gibert\Unity Projects\Bolt 2 test\Assets\Bolt\Bolt.Flow\Editor\Units\UnitGenerator.cs:162
— End of inner exception stack trace —

<!GraphPing[0,17940,4998a5c7-68e9-4918-befe-d03b569d4d71,724c2ba1-c3fd-467e-8e21-9f8d2a98b913]!>
UnityEngine.Debug:LogError(Object)
Unity.Bolt.<>c__DisplayClass2_0:<Generate>b__1(Task) (at Assets/Bolt/Bolt.Core/Editor/Generation/GenerationWorkflow.cs:92)
Unity.Bolt.Task:Run() (at Assets/Bolt/Bolt.Core/Editor/Tasks/Task.cs:66)
Unity.Bolt.WindowTaskRunner:RunSynchronous(Task) (at Assets/Bolt/Bolt.Core/Editor/Tasks/Runners/WindowTaskRunner.cs:62)
Unity.Bolt.<>c__DisplayClass10_0:<Run>b__0() (at Assets/Bolt/Bolt.Core/Editor/Tasks/Runners/WindowTaskRunner.cs:34)
System.Threading.ThreadHelper:ThreadStart()
{code}