[ci] fix builds on main branch (#1303)

Context: https://devdiv.visualstudio.com/DevDiv/DevDiv%20Team/_build/results?buildId=12682126&view=logs&j=784e4eae-0a8d-50ee-7be1-df4337debdeb&t=d146df5a-97f5-55ed-d881-1a15f3c31d98&l=3730

Builds on main are failing on Windows with:

    Starting a Gradle Daemon (subsequent builds will be faster)
    Warning: SDK processing. package.xml parsing problem. unrecognized type name: platform. Did you mean archives?
    Warning: SDK processing. package.xml parsing problem. Unable to create an instance of com.android.repository.impl.generated.v2.TypeDetails
    java.lang.InstantiationException...

Copilot suggested deleting all `package.xml` files from the Android
SDK installation.

I also updated the instructions to require Microsoft OpenJDK 21,
since that is what we are using now.

Author: jonathanpeppers

.github/copilot-instructions.md

@@ -33,7 +33,7 @@ The repository uses a **config-driven approach** where all bindings are defined
 ### Prerequisites
 - a recent .NET SDK
 - Cake .NET Tool: `dotnet tool install -g cake.tool`
-- Microsoft OpenJDK 11 (JDK-17 not supported)
+- Microsoft OpenJDK 21
 - Android SDK and `$ANDROID_SDK_ROOT` environment variable
 - Optional: `api-tools` for API diffs: `dotnet tool install -g api-tools`
 

build/ci/setup-environment.yml

@@ -90,4 +90,19 @@ steps:
       Write-Host "##vso[task.setvariable variable=ANDROID_HOME]${{ parameters.androidSdkRoot }}"
     displayName: Set ANDROID_SDK_ROOT and ANDROID_HOME to ${{ parameters.androidSdkRoot }}
 
+  - pwsh: |
+      # Remove problematic package.xml files that cause JAXB parsing issues with Java 21 on Windows
+      $androidSdkRoot = if ($env:ANDROID_SDK_ROOT) { $env:ANDROID_SDK_ROOT } else { $env:ANDROID_HOME }
+      if ($androidSdkRoot -and (Test-Path $androidSdkRoot)) {
+        Write-Host "Removing package.xml files from: $androidSdkRoot"
+        $files = Get-ChildItem -Path $androidSdkRoot -Filter "package.xml" -Recurse -ErrorAction SilentlyContinue
+        $files | Remove-Item -Force -ErrorAction SilentlyContinue
+        Write-Host "Removed $($files.Count) package.xml files"
+      } else {
+        Write-Host "Android SDK not found, skipping cleanup"
+      }
+    displayName: Clean Android SDK package.xml files
+    condition: eq(variables['Agent.OS'], 'Windows_NT')
+    continueOnError: true
+