Run GenerateAvaloniaResources before _InjectAvaloniaAdditionalFiles (#22175)

GenerateAvaloniaResources adds AvaloniaXaml items to AvaloniaResource, which
_InjectAvaloniaAdditionalFiles then reads to build AvaloniaResourcePaths.
Nothing ordered the two, so the property could be built from a partial list
depending on which target MSBuild scheduled first.

packages/Avalonia/AvaloniaBuildTasks.targets

@@ -39,7 +39,11 @@
                       Condition="'$(ApplicationIcon)' != ''" />
   </ItemGroup>
 
-  <Target Name="_InjectAvaloniaAdditionalFiles" BeforeTargets="GenerateMSBuildEditorConfigFileShouldRun">
+  <!-- GenerateAvaloniaResources adds AvaloniaXaml to AvaloniaResource, so it has to run first
+       or the items read below are incomplete. -->
+  <Target Name="_InjectAvaloniaAdditionalFiles"
+          BeforeTargets="GenerateMSBuildEditorConfigFileShouldRun"
+          DependsOnTargets="GenerateAvaloniaResources">
     <!-- Include AvaloniaXaml and AvaloniaResource (XAML only) as a Roslyn-visible additional files. -->
     <!-- This is necessary to use these files in source generators and other Roslyn-based extension. -->
     <!-- AdditionalFiles ensures that each file has Compilation available for them. -->