Add multitarget with old sdk

Avalonia.sln

@@ -107,7 +107,7 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Interop", "Interop", "{A0CC
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "RenderDemo", "samples\RenderDemo\RenderDemo.csproj", "{F1FDC5B0-4654-416F-AE69-E3E9BBD87801}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "ControlCatalog.Android", "samples\ControlCatalog.Android\ControlCatalog.Android.csproj", "{29132311-1848-4FD6-AE0C-4FF841151BD3}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ControlCatalog.Android", "samples\ControlCatalog.Android\ControlCatalog.Android.csproj", "{29132311-1848-4FD6-AE0C-4FF841151BD3}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Skia", "src\Skia\Avalonia.Skia\Avalonia.Skia.csproj", "{7D2D3083-71DD-4CC9-8907-39A0D86FB322}"
 EndProject

dirs.proj

@@ -11,7 +11,7 @@
     <ProjectReference Remove="src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github/**/*.*proj" />
     <ProjectReference Remove="tests/Avalonia.ReactiveUI.Events.UnitTests/Avalonia.ReactiveUI.Events.UnitTests.csproj" />
     <ProjectReference Remove="samples/ControlCatalog.Android/ControlCatalog.Android.csproj" />
-    <ProjectReference Remove="src/Android/Avalonia.AndroidTestApplication.csproj" />
+    <ProjectReference Remove="src/Android/Avalonia.AndroidTestApplication/Avalonia.AndroidTestApplication.csproj" />
   </ItemGroup>
   <ItemGroup Condition="!Exists('$(MSBuildExtensionsPath)\Xamarin\iOS')">
     <ProjectReference Remove="src/iOS/**/*.*proj" />

global.json

@@ -4,6 +4,7 @@
     },
     "msbuild-sdks": {
         "Microsoft.Build.Traversal": "1.0.43",
+        "Xamarin.Legacy.Sdk": "0.1.2-alpha6",
         "MSBuild.Sdk.Extras": "3.0.22",
         "AggregatePackage.NuGet.Sdk" : "0.1.12"
     }

src/Android/Avalonia.Android/Avalonia.Android.csproj

@@ -1,6 +1,6 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Xamarin.Legacy.Sdk">
   <PropertyGroup>
-    <TargetFramework>net6.0-android</TargetFramework>
+    <TargetFrameworks>net6.0-android;monoandroid11.0</TargetFrameworks>
     <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <MSBuildEnableWorkloadResolver>true</MSBuildEnableWorkloadResolver>