[Xamarin.Android.Build.Tasks] Bundled multidex jar (#124)

* [msbuild] switch to bundled multidex jar

Android SDK had obsoleted multidex support components, so we'd rather
embed the jar directly in our SDK.

* Copy android-support-multidex.jar into mandroid directory.

What this change actually does are:

- additionally download support m2repository in android-toolchains.
- extract multidex jar from support multidex aar.
- extend UnzipDirectoryChildren task to support non-children extraction.

* Copy support library license file to lib/mandroid as MULTIDEX_JAR_LICENSE.

It is to make it clear that the jar file is from Android SDK support library.

build-tools/android-toolchain/android-toolchain.projitems

@@ -78,6 +78,10 @@
       <HostOS></HostOS>
       <DestDir>platforms\android-24</DestDir>
     </AndroidSdkItem>
+    <AndroidSdkItem Include="android_m2repository_r16.zip">
+      <HostOS></HostOS>
+      <DestDir>extras\android\m2repository</DestDir>
+    </AndroidSdkItem>
   </ItemGroup>
   <ItemGroup>
     <_NdkToolchain Include="arm-linux-androideabi-clang" Condition="$(AndroidSupportedTargetJitAbisForConditionalChecks.Contains(':armeabi:')) Or $(AndroidSupportedTargetJitAbisForConditionalChecks.Contains(':armeabi-v7a:')) Or $(AndroidSupportedTargetAotAbisForConditionalChecks.Contains (':win-armeabi:'))">

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.targets

@@ -1,9 +1,18 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <UsingTask TaskName="Xamarin.Android.Tools.BootstrapTasks.GenerateProfile" AssemblyFile="..\..\bin\Build$(Configuration)\Xamarin.Android.Tools.BootstrapTasks.dll" />
+  <UsingTask TaskName="Xamarin.Android.Tools.BootstrapTasks.UnzipDirectoryChildren" AssemblyFile="..\..\bin\Build$(Configuration)\Xamarin.Android.Tools.BootstrapTasks.dll" />
   <PropertyGroup>
     <_SharedRuntimeBuildPath Condition=" '$(_SharedRuntimeBuildPath)' == '' ">..\..\bin\$(Configuration)\lib\xbuild-frameworks\MonoAndroid\</_SharedRuntimeBuildPath>
     <_GeneratedProfileClass>$(IntermediateOutputPath)Profile.g.cs</_GeneratedProfileClass>
+    <BuildDependsOn>
+		$(BuildDependsOn);
+		_CopyExtractedMultiDexJar;
+    </BuildDependsOn>
+    <_AndroidSdkLocation>$(ANDROID_SDK_PATH)</_AndroidSdkLocation>
+    <_AndroidSdkLocation Condition="'$(_AndroidSdkLocation)'==''">$(AndroidToolchainDirectory)\sdk</_AndroidSdkLocation>
+    <_MultiDexAarInAndroidSdk>extras\android\m2repository\com\android\support\multidex\1.0.1\multidex-1.0.1.aar</_MultiDexAarInAndroidSdk>
+    <_SupportLicenseInAndroidSdk>extras\android\m2repository\NOTICE.txt</_SupportLicenseInAndroidSdk>
   </PropertyGroup>
   <ItemGroup>
     <_SharedRuntimeAssemblies Include="$(_SharedRuntimeBuildPath)v1.0\*.dll;$(_SharedRuntimeBuildPath)$(AndroidFrameworkVersion)\*.dll"/>
@@ -23,4 +32,19 @@
         Lines="$(_GeneratedProfileClass)"
         Overwrite="false"/>
   </Target>
+
+  <Target Name="_CopyExtractedMultiDexJar"
+    Inputs="$(_AndroidSdkLocation)\$(_MultiDexAarInAndroidSdk);$(_AndroidSdkLocation)\$(_SupportLicenseInAndroidSdk)"
+    Outputs="$(OutputPath)..\..\..\mandroid\android-support-multidex.jar;$(OutputPath)..\..\..\mandroid\MULTIDEX_JAR_LICENSE">
+    <UnzipDirectoryChildren
+      NoSubdirectory="true"
+      SourceFiles="$(_AndroidSdkLocation)\$(_MultiDexAarInAndroidSdk)"
+      DestinationFolder="$(IntermediateOutputPath)multidex-aar" />
+    <Copy
+      SourceFiles="$(IntermediateOutputPath)multidex-aar\classes.jar"
+      DestinationFiles="$(OutputPath)..\..\..\mandroid\android-support-multidex.jar" />
+    <Copy
+      SourceFiles="$(_AndroidSdkLocation)\$(_SupportLicenseInAndroidSdk)"
+      DestinationFiles="$(OutputPath)..\..\..\mandroid\MULTIDEX_JAR_LICENSE" />
+  </Target>
 </Project>

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets

@@ -195,7 +195,8 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
 	<DeployExternal Condition="'$(DeployExternal)' == ''">False</DeployExternal>
 	<UseShortFileNames Condition="'$(UseShortFileNames)' != 'True'">False</UseShortFileNames>
 
-	<AndroidMultiDexSupportJar>extras\android\support\multidex\library\libs\android-support-multidex.jar</AndroidMultiDexSupportJar>
+	<!-- Obsolete build property: should be removed in the future releases -->
+	<AndroidMultiDexSupportJar></AndroidMultiDexSupportJar>
 
 	<AndroidSupportedAbis Condition=" '$(AndroidSupportedAbis)' == '' ">armeabi-v7a</AndroidSupportedAbis>
 
@@ -1072,7 +1073,11 @@ because xbuild doesn't support framework reference assemblies.
 
 <Target Name="_AddMultiDexDependencyJars">
 	<CreateItem Include="$(AndroidSdkDirectory)\$(AndroidMultiDexSupportJar)"
-		Condition="'$(AndroidEnableMultiDex)' == 'True'">
+		Condition="'$(AndroidEnableMultiDex)' == 'True' AND '$(AndroidMultiDexSupportJar)' != ''">
+      <Output TaskParameter="Include" ItemName="AndroidJavaLibrary" />
+	</CreateItem>
+	<CreateItem Include="$(MonoAndroidToolsDirectory)\android-support-multidex.jar"
+		Condition="'$(AndroidEnableMultiDex)' == 'True' AND '$(AndroidMultiDexSupportJar)' == ''">
       <Output TaskParameter="Include" ItemName="AndroidJavaLibrary" />
 	</CreateItem>
 </Target>

src/Xamarin.Android.Tools.BootstrapTasks/Xamarin.Android.Tools.BootstrapTasks/UnzipDirectoryChildren.cs

@@ -29,6 +29,8 @@ public UnzipDirectoryChildren ()
 		[Required]
 		public  ITaskItem       DestinationFolder   { get; set; }
 
+		public bool NoSubdirectory { get; set; }
+
 		public override bool Execute ()
 		{
 			Log.LogMessage (MessageImportance.Low, "Unzip:");
@@ -101,7 +103,9 @@ async TTask ExtractFile (string tempDir, string sourceFile, string relativeDestD
 				p.WaitForExit ();
 			}
 
-			foreach (var dir in Directory.EnumerateDirectories (nestedTemp, "*")) {
+			var dirs = NoSubdirectory ? new string [] { nestedTemp } : Directory.EnumerateDirectories (nestedTemp, "*");
+
+			foreach (var dir in dirs) {
 				foreach (var fse in Directory.EnumerateFileSystemEntries (dir)) {
 					var name    = Path.GetFileName (fse);
 					var destDir = string.IsNullOrEmpty (relativeDestDir)