[Xamarin.Android.Build.Tasks] default to only 64-bit targets (#9179)

We currently build for all 4 Android architectures by default.  While
modern apps are more likely to run on `android-arm64` modern devices
or `android-x64` default emulator on x64 machines.

Let's drop 32-bit targets by default, and let customers opt into them.
This could significatly help `Release` build times, etc.

Customers could opt into all 4 by adding in their `.csproj`:

	<RuntimeIdentifiers>android-arm;android-arm64;android-x86;android-x64</RuntimeIdentifiers>

Or in the case of a multi-targeted .NET MAUI project:

	<RuntimeIdentifiers Condition="$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)')) == 'android'">android-arm;android-arm64;android-x86;android-x64</RuntimeIdentifiers>

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.DefaultProperties.targets

@@ -87,7 +87,7 @@
     <SuppressTrimAnalysisWarnings Condition=" '$(SuppressTrimAnalysisWarnings)' == '' and ('$(TrimMode)' == 'full' or '$(IsAotCompatible)' == 'true') ">false</SuppressTrimAnalysisWarnings>
     <SuppressTrimAnalysisWarnings Condition=" '$(SuppressTrimAnalysisWarnings)' == '' ">true</SuppressTrimAnalysisWarnings>
     <!-- Prefer $(RuntimeIdentifiers) plural -->
-    <RuntimeIdentifiers Condition=" '$(RuntimeIdentifier)' == '' And '$(RuntimeIdentifiers)' == '' ">android-arm;android-arm64;android-x86;android-x64</RuntimeIdentifiers>
+    <RuntimeIdentifiers Condition=" '$(RuntimeIdentifier)' == '' And '$(RuntimeIdentifiers)' == '' ">android-arm64;android-x64</RuntimeIdentifiers>
     <RuntimeIdentifier  Condition=" '$(RuntimeIdentifiers)' != '' And '$(RuntimeIdentifier)' != '' " />
     <AndroidManifest Condition=" '$(AndroidManifest)' == '' and Exists ('Properties\AndroidManifest.xml') and !Exists ('AndroidManifest.xml') ">Properties\AndroidManifest.xml</AndroidManifest>
     <AndroidManifest Condition=" '$(AndroidManifest)' == '' ">AndroidManifest.xml</AndroidManifest>

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/AotTests.cs

@@ -282,14 +282,6 @@ public void BuildAMassiveApp ()
 			app1.Imports.Add (new Import ("foo.targets") {
 				TextContent = () => @"<?xml version=""1.0"" encoding=""utf-16""?>
 <Project ToolsVersion=""4.0"" xmlns=""http://schemas.microsoft.com/developer/msbuild/2003"">
-<Target Name=""_CheckAbis"" BeforeTargets=""_DefineBuildTargetAbis"">
-	<PropertyGroup>
-		<AndroidSupportedAbis>armeabi-v7a;x86</AndroidSupportedAbis>
-		<AndroidSupportedAbis Condition=""Exists('$(MSBuildThisFileDirectory)..\..\..\..\Debug\lib\xamarin.android\xbuild\Xamarin\Android\lib\arm64-v8a\libmono-android.release.so')"">$(AndroidSupportedAbis);arm64-v8a</AndroidSupportedAbis>
-		<AndroidSupportedAbis Condition=""Exists('$(MSBuildThisFileDirectory)..\..\..\..\Debug\lib\xamarin.android\xbuild\Xamarin\Android\lib\x86_64\libmono-android.release.so')"">$(AndroidSupportedAbis);x86_64</AndroidSupportedAbis>
-	</PropertyGroup>
-	<Message Text=""$(AndroidSupportedAbis)"" />
-</Target>
 <Target Name=""_Foo"" AfterTargets=""_SetLatestTargetFrameworkVersion"">
 	<PropertyGroup>
 		<AotAssemblies Condition=""!Exists('$(MonoAndroidBinDirectory)" + Path.DirectorySeparatorChar + @"cross-arm')"">False</AotAssemblies>

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/BuildWithLibraryTests.cs

@@ -152,7 +152,7 @@ public Foo ()
 			});
 			libB.OtherBuildItems.Add (new AndroidItem.AndroidNativeLibrary (default (Func<string>)) {
 				Update = () => "libfoo.so",
-				MetadataValues = "Link=x86\\libfoo.so",
+				MetadataValues = "Link=x86_64\\libfoo.so",
 				BinaryContent = () => Array.Empty<byte> (),
 			});
 			libB.AddReference (libC);
@@ -183,7 +183,7 @@ public Foo ()
 				aar.AssertContainsEntry (aarPath, "libs/A1AFA985571E728E.jar");
 				aar.AssertContainsEntry (aarPath, $"libs/{projectJarHash}.jar");
 				aar.AssertContainsEntry (aarPath, "jni/arm64-v8a/libfoo.so");
-				aar.AssertContainsEntry (aarPath, "jni/x86/libfoo.so");
+				aar.AssertContainsEntry (aarPath, "jni/x86_64/libfoo.so");
 				// proguard.txt from Library C should not flow to Library B and "double"
 				aar.AssertEntryEquals (aarPath, "proguard.txt", "# LibraryB");
 			}
@@ -223,7 +223,7 @@ public Foo ()
 				apk.AssertContainsEntry (aarPath, "res/layout/mylayout.xml");
 				apk.AssertContainsEntry (apkPath, "res/raw/bar.txt");
 				apk.AssertContainsEntry (apkPath, "lib/arm64-v8a/libfoo.so");
-				apk.AssertContainsEntry (apkPath, "lib/x86/libfoo.so");
+				apk.AssertContainsEntry (apkPath, "lib/x86_64/libfoo.so");
 			}
 
 			// Check classes.dex contains foo.jar
@@ -242,7 +242,7 @@ public Foo ()
 			Assert.IsTrue (DexUtils.ContainsClass (className, dexFile, AndroidSdkPath), $"`{dexFile}` should include `{className}`!");
 
 			// Check environment variable
-			var environmentFiles = EnvironmentHelper.GatherEnvironmentFiles (intermediate, "x86", required: true);
+			var environmentFiles = EnvironmentHelper.GatherEnvironmentFiles (intermediate, "x86_64", required: true);
 			var environmentVariables = EnvironmentHelper.ReadEnvironmentVariables (environmentFiles);
 			Assert.IsTrue (environmentVariables.TryGetValue (env_var, out string actual), $"Environment should contain {env_var}");
 			Assert.AreEqual (env_val, actual, $"{env_var} should be {env_val}");

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/LinkerTests.cs

@@ -661,6 +661,7 @@ public abstract class MyRunner {
 }"
 			});
 			var proj = new XamarinAndroidApplicationProject { IsRelease = true, ProjectName = "App1" };
+			proj.SetRuntimeIdentifiers(["armeabi-v7a", "arm64-v8a", "x86", "x86_64"]);
 			proj.References.Add(new BuildItem.ProjectReference (Path.Combine ("..", "Lib1", "Lib1.csproj"), "Lib1"));
 			proj.MainActivity = proj.DefaultMainActivity.Replace (
 				"base.OnCreate (bundle);",