Reduce the element of surprise in XAML compiler

src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.cs

@@ -46,7 +46,9 @@ namespace Avalonia.Build.Tasks
             string output, bool verifyIl, MessageImportance logImportance, string strongNameKey, bool patchCom,
             bool skipXamlCompilation)
         {
-            var typeSystem = new CecilTypeSystem(references.Concat(new[] { input }), input);
+            var typeSystem = new CecilTypeSystem(references
+                .Where(r => !r.ToLowerInvariant().EndsWith("avalonia.build.tasks.dll"))
+                .Concat(new[] { input }), input);
             
             var asm = typeSystem.TargetAssemblyDefinition;
 

src/Markup/Avalonia.Markup.Xaml.Loader/Avalonia.Markup.Xaml.Loader.csproj

@@ -4,6 +4,7 @@
     <TargetFramework>netstandard2.0</TargetFramework>
     <IsPackable>true</IsPackable>
     <PackageId>Avalonia.Markup.Xaml.Loader</PackageId>
+    <DefineConstants>$(DefineConstants);XAMLX_INTERNAL</DefineConstants>
   </PropertyGroup>
   <Import Project="IncludeXamlIlSre.props" />
   <ItemGroup>