[mtouch] Fix --dot:<path> to honor the path passed. (#5626)

Also change output to use the full path to files as nodes, instead of just the
filename, and instead use a label to set what's shown to just the filename.

This makes the graph correct when we have multiple files with the same name,
but different paths.

tools/common/BuildTasks.cs

@@ -74,7 +74,7 @@ namespace Xamarin.Bundler
 				throw new AggregateException (exceptions);
 		}
 
-		public void Dot (string file)
+		public void Dot (Application app, string file)
 		{
 			var nodes = new HashSet<string> ();
 			var queue = new Queue<BuildTask> (this);
@@ -82,12 +82,17 @@ namespace Xamarin.Bundler
 			var action_nodes = new HashSet<string> ();
 			var output_nodes = new HashSet<string> ();
 			var all_nodes = new HashSet<string> ();
+			var all_files = new HashSet<string> ();
 			var circular_ref_nodes = new HashSet<string> ();
 
 			var render_file = new Func<string, string> ((v) =>
 			{
 				if (Path.GetDirectoryName (v).EndsWith (".framework", StringComparison.Ordinal))
-					return Path.GetFileName (Path.GetDirectoryName (v));
+					v = Path.GetDirectoryName (v);
+				var cache = v.IndexOf (app.Cache.Location, StringComparison.Ordinal);
+				if (cache >= 0)
+					return v.Substring (app.Cache.Location.Length).TrimStart (Path.DirectorySeparatorChar);
+
 				return Path.GetFileName (v);
 			});
 
@@ -110,22 +115,28 @@ namespace Xamarin.Bundler
 				action_nodes.Add (action_node);
 
 				var inputs = task.Inputs.ToArray ();
+				all_files.UnionWith (inputs);
 				for (int i = 0; i < inputs.Length; i++) {
-					var node = $"\"{render_file (inputs [i])}\"";
+					var node = $"\"{inputs [i]}\"";
 					all_nodes.Add (node);
 					input_nodes.Add (node);
 					nodes.Add ($"{node} -> {action_node}");
 				}
 
 				var outputs = task.Outputs.ToArray ();
+				all_files.UnionWith (outputs);
 				for (int i = 0; i < outputs.Length; i++) {
-					var node = $"\"{render_file (outputs [i])}\"";
+					var node = $"\"{outputs [i]}\"";
 					all_nodes.Add (node);
 					output_nodes.Add (node);
 					nodes.Add ($"{action_node} -> {node}");
 				}
 			}
 
+			foreach (var af in all_files) {
+				nodes.Add ($"\"{af}\" [label=\"{render_file (af)}\"]");
+			}
+
 			using (var writer = new StreamWriter (file)) {
 				writer.WriteLine ("digraph build {");
 				writer.WriteLine ("\trankdir=LR;");

tools/mtouch/Application.cs

@@ -890,8 +890,8 @@ namespace Xamarin.Bundler {
 			CompilePInvokeWrappers ();
 			BuildApp ();
 
-			if (Driver.Dot)
-				build_tasks.Dot (Path.Combine (Cache.Location, "build.dot"));
+			if (Driver.DotFile != null)
+				build_tasks.Dot (this, Driver.DotFile.Length > 0 ? Driver.DotFile : Path.Combine (Cache.Location, "build.dot"));
 
 			Driver.Watch ("Building build tasks", 1);
 			build_tasks.Execute ();

tools/mtouch/mtouch.cs

@@ -123,15 +123,15 @@ namespace Xamarin.Bundler
 		//
 		// Output generation
 		static bool force = false;
-		static bool dot;
+		static string dotfile;
 		static string cross_prefix = Environment.GetEnvironmentVariable ("MONO_CROSS_PREFIX");
 		static string extra_args = Environment.GetEnvironmentVariable ("MTOUCH_ENV_OPTIONS");
 
 		static int verbose = GetDefaultVerbosity ();
 
-		public static bool Dot {
+		public static string DotFile {
 			get {
-				return dot;
+				return dotfile;
 			}
 		}
 
@@ -919,7 +919,7 @@ namespace Xamarin.Bundler
 			{ "h|?|help", "Displays the help", v => SetAction (Action.Help) },
 			{ "version", "Output version information and exit.", v => SetAction (Action.Version) },
 			{ "f|force", "Forces the recompilation of code, regardless of timestamps", v=>force = true },
-			{ "dot:", "Generate a dot file to visualize the build tree.", v => dot = true },
+			{ "dot:", "Generate a dot file to visualize the build tree.", v => dotfile = v ?? string.Empty },
 			{ "cache=", "Specify the directory where object files will be cached", v => app.Cache.Location = v },
 			{ "aot=", "Arguments to the static compiler",
 				v => app.AotArguments = v + (v.EndsWith (",", StringComparison.Ordinal) ? String.Empty : ",") + app.AotArguments