enhance: test on Windows and fix what it found (#1348)

Adds a weekly and on-demand workflow that runs the cross-compiled tests on Windows Server 2025 Core in a [dockur/windows](https://github.com/dockur/windows) QEMU VM, and fixes the Windows bugs it found in host and UNC paths, env handling, shell quoting, post-task scripts, health checks, checkout, action symlinks, step summaries, Git client certificates and docker mode from a Windows host.

Host-mode steps now emit UTF-8, `bash` falls back to Git's bash instead of the WSL launcher, the runner can run as a native Windows service, steps can keep background helpers with `RUNNER_TRACKING_ID`, and Windows arm64 binaries are released.

Fixes: https://gitea.com/gitea/runner/issues/1339
Fixes: https://gitea.com/gitea/runner/issues/637
Fixes: https://gitea.com/gitea/runner/issues/1172
Fixes: https://gitea.com/gitea/runner/issues/347
Reviewed-on: https://gitea.com/gitea/runner/pulls/1348
Reviewed-by: bircni <[email protected]>

act/container/docker_build_test.go

@@ -50,7 +50,7 @@ func TestCreateBuildContextFollowsDockerignoreAndSymlinkedRootButKeepsDockerfile
 
 	contexts := []string{dir}
 	if link := filepath.Join(t.TempDir(), "link"); os.Symlink(dir, link) == nil {
-		contexts = append(contexts, link+string(filepath.Separator))
+		contexts = append(contexts, link, link+string(filepath.Separator))
 	}
 
 	for _, contextDir := range contexts {