[build] Support JDK-21 (#9672)

* [build] Support JDK-21

Context: #9651

PR #9651 demonstrated that it was fairly straightforward to use
JDK-21 on CI.  We don't want to fully bump to JDK-21, because we
still support building with JDK-17, so we *at minimum* need to run
tests on both JDK-17 and JDK-21.

As a "minimal introductory step", add support for JDK-21:

  * Update to Gradle 8.12, for harmony with dotnet/java-interop.

  * Update the `<Javac/>` task to use `javac --release N` when using
    JDK-17 and later.  JDK-11 doesn't support `javac --release`.
    (Why care about JDK-11?  Because .NET 8 still supports it, and
    this will make future cherry-picking easier.)

  * Set `$(LatestSupportedJavaVersion)`=21.0.99, which removes the
    XA0030 error which would result from using JDK-21.

  * Update `tools/workload-dependencies` to use
    `$(LatestSupportedJavaVersion)` property, instead of always using
    `$(JavaSdkVersion)+1`.

* Address comments.

build-tools/gradle/gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.10.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.12-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

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

@@ -121,6 +121,7 @@ It is shared between "legacy" binding projects and .NET 7+ projects.
         Jars="@(_BindingJavaLibrariesToCompile);@(_ReferenceJavaLibs)"
         JavacTargetVersion="$(JavacTargetVersion)"
         JavacSourceVersion="$(JavacSourceVersion)"
+        JdkVersion="$(_JdkVersion)"
         IntermediateOutputPath="$(IntermediateOutputPath)"
         AssemblyIdentityMapFile="$(_AndroidLibrayProjectAssemblyMapFile)"
     />
@@ -168,6 +169,7 @@ It is shared between "legacy" binding projects and .NET 7+ projects.
         Jars="@(_JavaLibrariesToCompile);@(_ReferenceJavaLibs)"
         JavacTargetVersion="$(JavacTargetVersion)"
         JavacSourceVersion="$(JavacSourceVersion)"
+        JdkVersion="$(_JdkVersion)"
         IntermediateOutputPath="$(IntermediateOutputPath)"
         AssemblyIdentityMapFile="$(_AndroidLibrayProjectAssemblyMapFile)"
     />

src/Xamarin.Android.Build.Tasks/Tasks/Javac.cs

@@ -27,6 +27,8 @@ public class Javac : JavaCompileToolTask
 		public string JavacTargetVersion { get; set; }
 		public string JavacSourceVersion { get; set; }
 
+		public string JdkVersion { get; set; }
+
 		public override string DefaultErrorCode => "JAVAC0000";
 
 		public override bool RunTask ()
@@ -60,12 +62,28 @@ protected override string GenerateCommandLineCommands ()
 			cmd.AppendSwitchIfNotNull ("-J-Dfile.encoding=", "UTF8");
 
 			cmd.AppendFileNameIfNotNull (string.Format ("@{0}", TemporarySourceListFile));
-			cmd.AppendSwitchIfNotNull ("-target ", JavacTargetVersion);
-			cmd.AppendSwitchIfNotNull ("-source ", JavacSourceVersion);
+
+			if (int.TryParse (JavacSourceVersion, out int sourceVersion) &&
+					int.TryParse (JavacTargetVersion, out int targetVersion) &&
+					JavacSupportsRelease ()) {
+				cmd.AppendSwitchIfNotNull ("--release ", Math.Max (sourceVersion, targetVersion).ToString ());
+			} else {
+				cmd.AppendSwitchIfNotNull ("-target ", JavacTargetVersion);
+				cmd.AppendSwitchIfNotNull ("-source ", JavacSourceVersion);
+			}
 
 			return cmd.ToString ();
 		}
 
+		bool JavacSupportsRelease ()
+		{
+			if (string.IsNullOrEmpty (JdkVersion)) {
+				return false;
+			}
+			var jdkVersion  = Version.Parse (JdkVersion);
+			return jdkVersion.Major >= 17;
+		}
+
 		protected override void WriteOptionsToResponseFile (StreamWriter sw)
 		{
 			var jars = new List<string> ();

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.props.in

@@ -17,7 +17,7 @@
 		<ImplicitlyExpandNETStandardFacades>false</ImplicitlyExpandNETStandardFacades>
 		<CopyNuGetImplementations Condition=" '$(CopyNuGetImplementations)' == ''">true</CopyNuGetImplementations>
 		<YieldDuringToolExecution Condition="'$(YieldDuringToolExecution)' == ''">true</YieldDuringToolExecution>
-		<LatestSupportedJavaVersion Condition="'$(LatestSupportedJavaVersion)' == ''">17.0.99</LatestSupportedJavaVersion>
+		<LatestSupportedJavaVersion Condition="'$(LatestSupportedJavaVersion)' == ''">21.0.99</LatestSupportedJavaVersion>
 		<AndroidVersionCodePattern Condition=" '$(AndroidUseLegacyVersionCode)' != 'True' And '$(AndroidVersionCodePattern)' == '' ">{abi}{versionCode:D5}</AndroidVersionCodePattern>
 		<AndroidResourceGeneratorTargetName>UpdateGeneratedFiles</AndroidResourceGeneratorTargetName>
 		<AndroidUseApkSigner Condition=" '$(AndroidUseApkSigner)' == '' ">True</AndroidUseApkSigner>

tools/workload-dependencies/Program.cs

@@ -14,6 +14,7 @@
 var CmdlineToolsVersion     = (string?) null;
 var BuildToolsVersion       = (string?) null;
 var JdkVersion              = (string?) null;
+var JdkMaxVersion           = (string?) null;
 var NdkVersion              = (string?) null;
 var PlatformToolsVersion    = (string?) null;
 var PlatformVersion         = (string?) null;
@@ -37,6 +38,9 @@
 	{ "jdk-version=",
 	  "The JDK {VERSION} dotnet/android is built against.",
 	  v => JdkVersion = v },
+	{ "jdk-max-version=",
+	  "The maximum JDK {VERSION} dotnet/android supports.",
+	  v => JdkMaxVersion = v },
 	{ "ndk-version=",
 	  "The Android NDK {VERSION} dotnet/android is built against.",
 	  v => NdkVersion = v },
@@ -160,7 +164,7 @@ JProperty CreateJdkProperty (XDocument doc)
 {
 	var v               = new Version (JdkVersion ?? "17.0");
 	var start           = new Version (v.Major, v.Minor);
-	var end             = new Version (v.Major+1, 0);
+	var end             = GetMaxJdkVersion (v);
 	var latestRevision  = JdkVersion ?? GetLatestRevision (doc, "jdk");
 	var contents        = new JObject (
 		new JProperty ("version", $"[{start},{end})"));
@@ -169,6 +173,17 @@ JProperty CreateJdkProperty (XDocument doc)
 	return new JProperty ("jdk", contents);
 }
 
+string GetMaxJdkVersion (Version v)
+{
+	if (!string.IsNullOrEmpty (JdkMaxVersion)) {
+		// JdkMaxVersion is `$(LatestSupportedJavaVersion)`, which is still a supported version!
+		// Return the major version past JdkMaxVersion
+		var x   = new Version (JdkMaxVersion);
+		return new Version (x.Major+1, 0).ToString ();
+	}
+	return new Version (v.Major+1, 0).ToString ();
+}
+
 IEnumerable<XElement> GetSupportedElements (XDocument doc, string element)
 {
 	if (doc.Root == null) {

tools/workload-dependencies/WorkloadDependencies.proj

@@ -69,6 +69,7 @@
       <_WorkloadDeps Include="--build-tools-version=$(AndroidSdkBuildToolsVersion)" />
       <_WorkloadDeps Include="--cmdline-tools-version=$(AndroidCommandLineToolsVersion)" />
       <_WorkloadDeps Include="--jdk-version=$(JavaSdkVersion)" />
+      <_WorkloadDeps Include="--jdk-max-version=$(LatestSupportedJavaVersion)" />
       <_WorkloadDeps Include="--ndk-version=$(AndroidNdkVersion)" />
       <_WorkloadDeps Include="--platform-tools-version=$(AndroidSdkPlatformToolsVersion)" />
       <_WorkloadDeps Include="--platform-version=$(AndroidSdkPlatformVersion)" />