[msbuild] Port the BTouch task to subclass XamarinTask. (#21616)

This has a few advantages:

* We simplify and unify more of our code.
* We have more control over the error reporting / logging behavior.

Additionally:

* Rename the tool to 'BGen', since that's what the .NET version of the tool is called, and update properties and item groups accordingly.
* Allow for overriding the path to the command-line tool in question.
* Add support for cancellation.
* Fix nullability.
* Add documentation for the relevant properties and item groups.

docs/build-apps/build-items.md

@@ -30,6 +30,13 @@ See also:
 * The [AppIcon](build-properties.md#AppIcon) property.
 * The [IncludeAllAppIcons](build-properties.md#IncludeAllAppIcons) property.
 
+## BGenReferencePath
+
+The list of assembly references to pass to the `bgen` tool (binding generator).
+
+Typically this is handled automatically by adding references as
+`ProjectReference` or `PackageReference` items instead.
+
 ## PartialAppManifest
 
 `PartialAppManifest` can be used to add additional partial app manifests that

docs/build-apps/build-properties.md

@@ -39,6 +39,28 @@ See also:
 * The [AlternateAppIcon](build-items.md#AlternateAppIcon) item group.
 * The [IncludeAllAppIcons](#IncludeAllAppIcons) property.
 
+### BGenEmitDebugInformation
+
+Whether the `bgen` tool (the binding generator) should emit debug information or not.
+
+The default behavior is `true` when the `Debug` property is set to `true`.
+
+## BGenExtraArgs
+
+Any extra arguments to the `bgen` tool (the binding generator).
+
+## BGenToolExe
+
+The name of the `bgen` executable (a tool used by binding projects to generate bindings).
+
+The default behavior is to use the `bgen` tool shipped with our workload.
+
+## BGenToolPath
+
+The directory to where the `bgen` ([BGenToolExe](#BGenToolExe)) is located.
+
+The default behavior is to use the `bgen` tool shipped with our workload.
+
 ## DittoPath
 
 The full path to the `ditto` executable.

dotnet/targets/Xamarin.Shared.Sdk.targets

@@ -1416,8 +1416,8 @@
 
 	<Target Name="_ComputeBindingVariables" DependsOnTargets="_ComputeFrameworkVariables" Condition="'$(IsBindingProject)' == 'true'">
 		<PropertyGroup>
-			<BTouchToolExe>bgen.dll</BTouchToolExe>
-			<BTouchToolPath>$(_XamarinSdkRootDirectory)\tools\lib\bgen</BTouchToolPath>
+			<BGenToolExe>bgen.dll</BGenToolExe>
+			<BGenToolPath>$(_XamarinSdkRootDirectory)\tools\lib\bgen</BGenToolPath>
 			<BaseLibDllPath>$(_XamarinRefAssemblyPath)</BaseLibDllPath>
 			<_GeneratorAttributeAssembly>$(_XamarinSdkRootDirectory)/tools/lib/Xamarin.Apple.BindingAttributes.dll</_GeneratorAttributeAssembly>
 			<_DotNetCscCompiler>$(RoslynTargetsPath)\bincore\csc.dll</_DotNetCscCompiler>

msbuild/Xamarin.MacDev.Tasks/CommandLineArgumentBuilder.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Linq;
 using System.Text;
 using System.Collections.Generic;
 
@@ -229,5 +230,32 @@ public string CreateResponseFile (Task task, string responseFilePath, IList<stri
 			// Generate the command line
 			return actualArgs.ToString ();
 		}
+
+		public static List<string> CreateResponseFile (Task task, string responseFilePath, IList<string> responseArguments, IList<string> nonResponseArguments)
+		{
+			// Generate a response file
+			var responseFile = Path.GetFullPath (responseFilePath);
+
+			if (File.Exists (responseFile))
+				File.Delete (responseFile);
+
+			try {
+				File.WriteAllLines (responseFile, StringUtils.Quote (responseArguments.ToArray ()));
+			} catch (Exception ex) {
+				task.Log.LogWarning ("Failed to create response file '{0}': {1}", responseFile, ex);
+			}
+
+			// Some arguments can not safely go in the response file and are 
+			// added separately. They must go _after_ the response file
+			// as they may override options passed in the response file
+			var actualArgs = new List<string> ();
+
+			actualArgs.Add ($"@{responseFile}");
+			if (nonResponseArguments is not null)
+				actualArgs.AddRange (nonResponseArguments);
+
+			// Generate the command line
+			return actualArgs;
+		}
 	}
 }