[MSBuild] Use delegate instead of Func for start process handler

Using a delegate makes it clearer what the arguments for the method
are.

Author: mrward

main/src/core/MonoDevelop.Core/MonoDevelop.Projects.MSBuild/MSBuildProcessService.cs

@@ -34,11 +34,12 @@ namespace MonoDevelop.Projects.MSBuild
 {
 	public static class MSBuildProcessService
 	{
+		public delegate ProcessWrapper StartProcessCallback (string command, string arguments, string workingDirectory, TextWriter outWriter, TextWriter errorWriter, EventHandler exited);
+
 		/// <summary>
 		/// Allows the MSBuild process start to be intercepted and monitored.
 		/// </summary>
-		public static Func<string, string, string, TextWriter, TextWriter, EventHandler, ProcessWrapper>
-			StartProcessHandler { get; set; } = Runtime.ProcessService.StartProcess;
+		public static StartProcessCallback StartProcessHandler { get; set; } = Runtime.ProcessService.StartProcess;
 
 		public static ProcessWrapper StartMSBuild (string arguments, string workingDirectory, TextWriter outWriter, TextWriter errorWriter, EventHandler exited)
 		{