Support cache (#25)

See [Caching dependencies to speed up workflows](https://docs.github.com/en/actions/using-workflows/caching-dependencies-to-speed-up-workflows).

Reviewed-on: https://gitea.com/gitea/act_runner/pulls/25
Reviewed-by: Lunny Xiao <[email protected]>
Reviewed-by: Zettat123 <[email protected]>
Co-authored-by: Jason Song <[email protected]>
Co-committed-by: Jason Song <[email protected]>

runtime/runtime.go

@@ -8,6 +8,8 @@ import (
 	"strings"
 
 	runnerv1 "code.gitea.io/actions-proto-go/runner/v1"
+
+	"gitea.com/gitea/act_runner/artifactcache"
 	"gitea.com/gitea/act_runner/client"
 )
 
@@ -18,11 +20,17 @@ type Runner struct {
 	Environ       map[string]string
 	Client        client.Client
 	Labels        []string
+	CacheHandler  *artifactcache.Handler
 }
 
 // Run runs the pipeline stage.
 func (s *Runner) Run(ctx context.Context, task *runnerv1.Task) error {
-	return NewTask(s.ForgeInstance, task.Id, s.Client, s.Environ, s.platformPicker).Run(ctx, task)
+	env := map[string]string{}
+	for k, v := range s.Environ {
+		env[k] = v
+	}
+	env["ACTIONS_CACHE_URL"] = s.CacheHandler.ExternalURL() + "/"
+	return NewTask(s.ForgeInstance, task.Id, s.Client, env, s.platformPicker).Run(ctx, task)
 }
 
 func (s *Runner) platformPicker(labels []string) string {