CI: complete the Windows CI coverage

Extend the Windows CI to include the tests as well.  This will mostly
complete the Windows support (the remaining pieces remain in supporting
the Windows ARM64 build host).

Author: compnerd

.bazelci/presubmit.yml

@@ -40,12 +40,24 @@ x_defaults:
       - "-//test:output_file_map_default"
   windows_common: &windows_common
     platform: windows
+    environment:
+      SWIFT_VERSION: 6.1.0
+      PATH: "%LOCALAPPDATA%\\Programs\\Swift\\Toolchains\\%SWIFT_VERSION%+Asserts\\usr\\bin;%LOCALAPPDATA%\\Programs\\Swift\\Runtimes\\%SWIFT_VERSION%\\usr\\bin;%Path%"
+      SDKROOT: "%LOCALAPPDATA%\\Programs\\Swift\\Platforms\\%SWIFT_VERSION%\\Windows.platform\\Developer\\SDKs\\Windows.sdk"
     build_flags:
       # Override 'sandboxed' strategy set in .bazelrc because it's not
       # available on Windows
       - "--strategy=SwiftCompile="
+      - "--repo_env=SDKROOT=%LOCALAPPDATA%\\Programs\\Swift\\Platforms\\%SWIFT_VERSION%\\Windows.platform\\Developer\\SDKs\\Windows.sdk"
+      - "--repo_env=Path=%LOCALAPPDATA%\\Programs\\Swift\\Toolchains\\%SWIFT_VERSION%+Asserts\\usr\\bin;%LOCALAPPDATA%\\Programs\\Swift\\Runtimes\\%SWIFT_VERSION%\\usr\\bin;%Path%"
     build_targets:
       - "//tools/..."
+    test_flags:
+     - "--compiler=clang-cl"
+    test_targets:
+      - "//examples/..."
+      - "-//examples/apple/..."
+      - "-//examples/xplatform/grpc/..." # TODO: Fix gRPC on Windows
 
 tasks:
   # TODO: Uncomment once Bazel 8 is released
@@ -118,11 +130,14 @@ tasks:
       - .bazelci/update_workspace_to_deps_heads.sh
     <<: *linux_common
 
-  # TODO: re-enable when Windows in Bazel CI is properly configured for Swift.
-  # windows_last_green:
-  #   name: "Last Green Bazel"
-  #   bazel: last_green
-  #   <<: *windows_common
+  windows_last_green:
+    name: "Last Green Bazel"
+    bazel: last_green
+    batch_commands:
+      - echo --- Downloading and installing Swift %SWIFT_VERSION%
+      - curl.exe -L https://download.swift.org/swift-6.1-release/windows10/swift-6.1-RELEASE/swift-6.1-RELEASE-windows10.exe -o %TEMP%\installer.exe
+      - PowerShell Start-Process -FilePath ${env:TEMP}\installer.exe -ArgumentList(\"/install\", \"/passive\", \"/norestart\", \"/log log.txt\") -Wait -PassThru -Verb RunAs
+    <<: *windows_common
 
   doc_tests:
     name: "Doc tests"