fix(exec): serve the v4 artifact API so upload-artifact v4 and later work (#1341)

`exec` forwarded the toolkit's ArtifactService calls to an instance it never registered, and its random runtime token held no backend IDs, so `actions/upload-artifact` and `actions/download-artifact` v4 and later failed.

The local artifact server now serves the v4 API, including the single Put Blob uploads docker/build-push-action uses. `exec` gives each workflow its own unsigned JWT runtime token and artifact run, so artifact names conflict and carry over between runs as on GitHub. Artifacts default to a temporary directory instead of the workspace that jobs copy.

Co-authored-by: silverwind <[email protected]>
Co-authored-by: Lunny Xiao <[email protected]>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1341
Reviewed-by: Lunny Xiao <[email protected]>
Reviewed-by: silverwind <[email protected]>
Co-authored-by: bircni <[email protected]>

e2e/main_test.go

@@ -6,11 +6,15 @@
 package e2e
 
 import (
+	"cmp"
 	"context"
 	"fmt"
 	"os"
+	"os/exec"
+	"path/filepath"
 	"regexp"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -25,6 +29,16 @@ var fixture *GiteaFixture
 
 var skipReason string
 
+var binDir string
+
+var runnerBinary = sync.OnceValues(func() (string, error) {
+	bin := filepath.Join(binDir, "gitea-runner")
+	if out, err := exec.Command(cmp.Or(os.Getenv("GO"), "go"), "build", "-o", bin, "..").CombinedOutput(); err != nil {
+		return "", fmt.Errorf("build runner: %w\n%s", err, out)
+	}
+	return bin, nil
+})
+
 func TestMain(m *testing.M) {
 	os.Exit(runSuite(m))
 }
@@ -47,6 +61,12 @@ func runSuite(m *testing.M) int {
 	fixture = f
 	defer func() { _ = fixture.Close(context.Background()) }()
 
+	if binDir, err = os.MkdirTemp("", "gitea-runner-e2e-"); err != nil {
+		fmt.Fprintf(os.Stderr, "create binary dir: %v\n", err)
+		return 1
+	}
+	defer os.RemoveAll(binDir)
+
 	fmt.Fprintf(os.Stderr, "gitea fixture: image=%s version=%s\n", fixture.image, fixture.version)
 
 	return m.Run()