Enable Android build in CI (no tests, only build). (#1382)

Enable the Android CI workflow added in
swiftlang/github-workflows#172.

### Checklist:

- [x] Code and documentation should follow the style of the [Style
Guide](https://github.com/apple/swift-testing/blob/main/Documentation/StyleGuide.md).
- [x] If public symbols are renamed or modified, DocC references should
be updated.

Author: grynspan

.github/workflows/pull_request.yml

@@ -24,6 +24,7 @@ jobs:
       enable_ios_checks: true
       ios_host_exclude_xcode_versions: '[{"xcode_version": "16.2"}, {"xcode_version": "16.3"}, {"xcode_version": "16.4"}]'
       enable_wasm_sdk_build: true
+      enable_android_sdk_build: true
   soundness:
     name: Soundness
     uses: swiftlang/github-workflows/.github/workflows/soundness.yml@main