Update legacy projects targets

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

@@ -1,6 +1,7 @@
 <Project Sdk="Xamarin.Legacy.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>net6.0-android;monoandroid11.0</TargetFrameworks>
+    <TargetFrameworks>net6.0-android</TargetFrameworks>
+    <TargetFrameworks Condition="'$(MSBuildRuntimeType)' != 'Core'">net6.0-ios;monoandroid11.0</TargetFrameworks>
     <SupportedOSPlatformVersion>21</SupportedOSPlatformVersion>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <MSBuildEnableWorkloadResolver>true</MSBuildEnableWorkloadResolver>

src/iOS/Avalonia.iOS/Avalonia.iOS.csproj

@@ -1,8 +1,9 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Xamarin.Legacy.Sdk">
   <PropertyGroup>
-    <TargetFramework>net6.0-ios</TargetFramework>
-    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+    <TargetFrameworks>net6.0-ios</TargetFrameworks>
+    <TargetFrameworks Condition="'$(MSBuildRuntimeType)' != 'Core'">$(TargetFrameworks);xamarin.ios10</TargetFrameworks>
     <SupportedOSPlatformVersion>10.0</SupportedOSPlatformVersion>
+    <MSBuildEnableWorkloadResolver>true</MSBuildEnableWorkloadResolver>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\Avalonia.Base\Avalonia.Base.csproj" />