[msbuild] Improve the Strip task.

* Enable nullability and fix code accordingly.
* Augment it to be able to take multiple files to strip at the same time.
* Strip in parallel.
* Execute using xcrun (ref: xamarin#3931)
* Pass the full path to the executable file to strip, to make command lines
  easier to copy-paste.
* Remove test that is now outdated. We have other tests that run strip
  anyways, so this shouldn't be a problem.

msbuild/Xamarin.MacDev.Tasks.Core/Tasks/CodesignTaskBase.cs

@@ -152,16 +152,6 @@ bool ParseBoolean (ITaskItem item, string metadataName, bool fallbackValue)
 			return string.Equals (metadataValue, "true", StringComparison.OrdinalIgnoreCase);
 		}
 
-		string GetNonEmptyStringOrFallback (ITaskItem item, string metadataName, string fallbackValue, string fallbackName = null, bool required = false)
-		{
-			var metadataValue = item.GetMetadata (metadataName);
-			if (!string.IsNullOrEmpty (metadataValue))
-				return metadataValue;
-			if (required && string.IsNullOrEmpty (fallbackValue))
-				Log.LogError (MSBStrings.E7085 /* The "{0}" task was not given a value for the required parameter "{1}", nor was there a "{2}" metadata on the resource {3}. */, "Codesign", fallbackName, metadataName, item.ItemSpec);
-			return fallbackValue;
-		}
-
 		IList<string> GenerateCommandLineArguments (ITaskItem item)
 		{
 			var args = new List<string> ();

msbuild/Xamarin.MacDev.Tasks.Core/Tasks/SymbolStripTaskBase.cs

@@ -1,64 +1,67 @@
 using System;
 using System.IO;
+using System.Collections.Generic;
+
+using Parallel = System.Threading.Tasks.Parallel;
+using ParallelOptions = System.Threading.Tasks.ParallelOptions;
 
 using Microsoft.Build.Framework;
-using Microsoft.Build.Utilities;
+
+#nullable enable
 
 namespace Xamarin.MacDev.Tasks
 {
-	public abstract class SymbolStripTaskBase : XamarinToolTask
+	public abstract class SymbolStripTaskBase : XamarinTask
 	{
 		#region Inputs
 
 		[Required]
-		public string Executable { get; set; }
+		public ITaskItem[] Executable { get; set; } = Array.Empty<ITaskItem> ();
 
-		public string SymbolFile { get; set; }
+		// This can also be specified as metadata on the Executable item (as 'SymbolFile')
+		public string SymbolFile { get; set; } = string.Empty;
 
-		[Required]
+		// This can also be specified as metadata on the Executable item  (as 'IsFramework')
 		public bool IsFramework { get; set; }
-
 		#endregion
 
-		protected override string ToolName {
-			get { return "strip"; }
-		}
-
-		protected override string GenerateFullPathToTool ()
+		bool GetIsFramework (ITaskItem item)
 		{
-			if (!string.IsNullOrEmpty (ToolPath))
-				return Path.Combine (ToolPath, ToolExe);
-
-			var path = Path.Combine (AppleSdkSettings.DeveloperRoot, "Toolchains", "XcodeDefault.xctoolchain", "usr", "bin", ToolExe);
-
-			return File.Exists (path) ? path : ToolExe;
+			var value = GetNonEmptyStringOrFallback (item, "IsFramework", IsFramework ? "true" : "false", required: true);
+			return string.Equals (value, "true", StringComparison.OrdinalIgnoreCase);
 		}
 
-		protected override string GenerateCommandLineCommands ()
+		void ExecuteStrip (ITaskItem item)
 		{
-			var args = new CommandLineBuilder ();
+			var args = new List<string> ();
 
-			if (!string.IsNullOrEmpty (SymbolFile)) {
-				args.AppendSwitch ("-i");
-				args.AppendSwitch ("-s");
-				args.AppendFileNameIfNotNull (SymbolFile);
+			args.Add ("strip");
+
+			var symbolFile = GetNonEmptyStringOrFallback (item, "SymbolFile", SymbolFile);
+			if (!string.IsNullOrEmpty (symbolFile)) {
+				args.Add ("-i");
+				args.Add ("-s");
+				args.Add (symbolFile);
 			}
 
-			if (IsFramework) {
+			if (GetIsFramework (item)) {
 				// Only remove debug symbols from frameworks.
-				args.AppendSwitch ("-S");
-				args.AppendSwitch ("-x");
+				args.Add ("-S");
+				args.Add ("-x");
 			}
 
-			args.AppendFileNameIfNotNull (Executable);
+			args.Add (Path.GetFullPath (item.ItemSpec));
 
-			return args.ToString ();
+			ExecuteAsync ("xcrun", args).Wait ();
 		}
 
-		protected override void LogEventsFromTextOutput (string singleLine, MessageImportance messageImportance)
+		public override bool Execute ()
 		{
-			// TODO: do proper parsing of error messages and such
-			Log.LogMessage (messageImportance, "{0}", singleLine);
+			Parallel.ForEach (Executable, new ParallelOptions { MaxDegreeOfParallelism = Math.Max (Environment.ProcessorCount / 2, 1) }, (item) => {
+				ExecuteStrip (item);
+			});
+
+			return !Log.HasLoggedErrors;
 		}
 	}
 }

msbuild/Xamarin.MacDev.Tasks.Core/Tasks/XamarinTask.cs

@@ -152,5 +152,15 @@ protected void FileCopierLogCallback (int min_verbosity, string format, params o
 			}
 			Log.LogMessage (importance, format, arguments);
 		}
+
+		protected string GetNonEmptyStringOrFallback (ITaskItem item, string metadataName, string fallbackValue, string fallbackName = null, bool required = false)
+		{
+			var metadataValue = item.GetMetadata (metadataName);
+			if (!string.IsNullOrEmpty (metadataValue))
+				return metadataValue;
+			if (required && string.IsNullOrEmpty (fallbackValue))
+				Log.LogError (MSBStrings.E7085 /* The "{0}" task was not given a value for the required parameter "{1}", nor was there a "{2}" metadata on the resource {3}. */, GetType ().Name, fallbackName ?? metadataName, metadataName, item.ItemSpec);
+			return fallbackValue;
+		}
 	}
 }

msbuild/Xamarin.MacDev.Tasks/Tasks/SymbolStrip.cs

@@ -1,6 +1,7 @@
-using Microsoft.Build.Framework;
 using Xamarin.Messaging.Build.Client;
 
+#nullable enable
+
 namespace Xamarin.MacDev.Tasks
 {
 	public class SymbolStrip : SymbolStripTaskBase
@@ -12,13 +13,5 @@ public override bool Execute ()
 
 			return base.Execute ();
 		}
-
-		public override void Cancel ()
-		{
-			if (ShouldExecuteRemotely ())
-				BuildConnection.CancelAsync (SessionId, BuildEngine4).Wait ();
-
-			base.Execute ();
-		}
 	}
 }