Fix to workaround a Roslyn issue leaking instances of the InteractiveAssemblyLoader

Author: fabiocav

src/WebJobs.Script/Description/CSharp/CSharpFunctionInvoker.cs

@@ -19,6 +19,7 @@
 using Microsoft.CodeAnalysis.CSharp;
 using Microsoft.CodeAnalysis.CSharp.Scripting;
 using Microsoft.CodeAnalysis.Scripting;
+using Microsoft.CodeAnalysis.Scripting.Hosting;
 
 namespace Microsoft.Azure.WebJobs.Script.Description
 {
@@ -42,6 +43,9 @@ public class CSharpFunctionInvoker : ScriptFunctionInvokerBase
         private Action<MethodInfo, object[], object> _resultProcessor;
         private FunctionValueLoader _functionValueLoader;
 
+        private static readonly Lazy<InteractiveAssemblyLoader> AssemblyLoader
+            = new Lazy<InteractiveAssemblyLoader>(() => new InteractiveAssemblyLoader(), LazyThreadSafetyMode.ExecutionAndPublication);
+
         private static readonly string[] WatchedFileTypes = { ".cs", ".csx", ".dll", ".exe" };
 
         internal CSharpFunctionInvoker(ScriptHost host, FunctionMetadata functionMetadata,
@@ -407,7 +411,7 @@ private Compilation GetScriptCompilation(Script<object> script, bool debug)
         private Script<object> CreateScript()
         {
             string code = GetFunctionSource();
-            return CSharpScript.Create(code, options: _metadataResolver.FunctionScriptOptions);
+            return CSharpScript.Create(code, options: _metadataResolver.FunctionScriptOptions, assemblyLoader: AssemblyLoader.Value);
         }
 
         private static object GetTaskResult(Task task)