ci: fix release/stable/9.0 build against current SDK & runner images

The first full CI run on the 9.0 branch in a while (triggered by the #3407
navigation backport push) failed due to toolchain drift, not the backported
code itself:

- Maui & Uno fail with NETSDK1202: the net8.0 platform workloads
  (net8.0-android/ios/maccatalyst/macos) are now end-of-life, and the CI SDK
  (10.0.301) fails the build over it. Opt out of the EOL checks via
  CheckEolWorkloads/CheckEolTargetFramework - the 9.0 maintenance branch
  intentionally targets .NET 8 for its lifecycle.

- Forms fails because the Xamarin.Android (MonoAndroid) language targets ship
  only with Visual Studio's Xamarin component, which was dropped from
  windows-latest (VS 18) and windows-2025. Pin the Forms job to windows-2022,
  the last hosted image that still includes it.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dansiegel

.github/workflows/ci.yml

@@ -55,6 +55,10 @@ jobs:
   build-prism-forms:
     uses: avantipoint/workflow-templates/.github/workflows/msbuild-build.yml@v1
     with:
+      # Prism.Forms builds the Xamarin.Android (MonoAndroid) target, whose language targets
+      # ship only with Visual Studio's Xamarin component. That component was dropped from
+      # windows-latest (VS 18) and windows-2025, so pin to windows-2022 which still includes it.
+      runs-on: windows-2022
       name: Build Prism.Forms
       solution-path: PrismLibrary_Forms.slnf
       code-sign: true

Directory.Build.props

@@ -25,6 +25,15 @@
     </PolySharpIncludeGeneratedTypes>
     <WarningsAsErrors>$(WarningsAsErrors);IDE0003</WarningsAsErrors>
     <ImplicitUsings>enable</ImplicitUsings>
+    <!--
+      Prism 9.0 is a maintenance branch that intentionally targets .NET 8 and its platform
+      workloads (net8.0-android, net8.0-ios, net8.0-maccatalyst, net8.0-macos). Current .NET
+      SDKs flag these as end-of-life - NETSDK1202 for the workloads and NETSDK1138 for the
+      target framework - which fails the build. Opt out of the EOL checks so the branch keeps
+      building on current SDKs; shipping these targets for the 9.0 lifecycle is intentional.
+    -->
+    <CheckEolWorkloads>false</CheckEolWorkloads>
+    <CheckEolTargetFramework>false</CheckEolTargetFramework>
   </PropertyGroup>
 
   <PropertyGroup>