[bazel] Enable windows builds?

.github/workflows/bazel.yml

@@ -36,9 +36,10 @@ jobs:
             target: aarch64-unknown-linux-musl
           - os: ubuntu-24.04
             target: x86_64-unknown-linux-musl
-          # TODO: Enable Windows once we fix the toolchain issues there.
-          #- os: windows-latest
-          #  target: x86_64-pc-windows-gnullvm
+
+          # Windows
+          - os: windows-latest
+            target: x86_64-pc-windows-gnullvm
     runs-on: ${{ matrix.os }}
 
     # Configure a human readable name for each job
@@ -61,6 +62,14 @@ jobs:
         shell: pwsh
         run: Copy-Item (Get-Command dotslash).Source -Destination "$env:LOCALAPPDATA\Microsoft\WindowsApps\dotslash.exe"
 
+      - name: Where is git (pwsh)
+        if: runner.os == 'Windows'
+        shell: pwsh
+        run: |
+          Get-Command git | Format-List *
+          (Get-Command git).Source
+          where.exe git
+
       # Install Bazel via Bazelisk
       - name: Set up Bazel
         uses: bazelbuild/setup-bazelisk@v3
@@ -95,7 +104,7 @@ jobs:
         shell: pwsh
         run: |
           # Use a very short path to reduce argv/path length issues.
-          "BAZEL_STARTUP_ARGS=--output_user_root=C:\" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
+          "BAZEL_STARTUP_ARGS=--output_user_root=D:\" | Out-File -FilePath $env:GITHUB_ENV -Encoding utf8 -Append
 
       - name: bazel test //...
         env:

.github/workflows/ci.bazelrc

@@ -2,6 +2,15 @@ common --remote_download_minimal
 common --nobuild_runfile_links
 common --keep_going
 
+# By default runfiles directories are disabled on Windows but we
+# don't read runfiles manifests, so force them on.
+common --enable_runfiles
+
+# Rearrange caches on Windows so they're on the same volume as the checkout.
+common:windows --disk_cache=D:/a/.cache/bazel-disk-cache
+common:windows --repo_contents_cache=D:/a/.cache/bazel-repo-contents-cache
+common:windows --repository_cache=D:/a/.cache/bazel-repo-cache
+
 # We prefer to run the build actions entirely remotely so we can dial up the concurrency.
 # We have platform-specific tests, so we want to execute the tests on all platforms using the strongest sandboxing available on each platform.