fix: resolve container sleep through PATH (#1255)

Resolve the job container's sleep command through PATH so images with nonstandard binary locations, including Nix, can run jobs.

Closes https://gitea.com/gitea/runner/issues/808

---------

Co-authored-by: silverwind <me@silverwind.io>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1255
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>

act/runner/run_context.go

@@ -575,7 +575,7 @@ func (rc *RunContext) startJobContainer() common.Executor {
 		ext := container.LinuxContainerEnvironmentExtensions{}
 		containerInput := &container.NewContainerInput{
 			Cmd:             nil,
-			Entrypoint:      []string{"/bin/sleep", fmt.Sprint(rc.Config.ContainerMaxLifetime.Round(time.Second).Seconds())},
+			Entrypoint:      []string{"sleep", fmt.Sprint(rc.Config.ContainerMaxLifetime.Round(time.Second).Seconds())},
 			WorkingDir:      ext.ToContainerPath(rc.Config.Workdir),
 			Image:           image,
 			Username:        username,

act/runner/run_context_test.go

@@ -343,7 +343,7 @@ jobs:
 	require.Nil(t, redis.Cmd)
 }
 
-func TestStartJobContainerEvaluatesContainersOnceAndTrimsDockerPrefix(t *testing.T) {
+func TestStartJobContainerBuildsEvaluatedJobAndServiceInputs(t *testing.T) {
 	inputs := startJobContainerInputs(t, `
 jobs:
   job:
@@ -359,6 +359,7 @@ jobs:
 	require.Equal(t, []string{"/entry.sh"}, redis.Entrypoint)
 	require.Equal(t, []string{"redis-server", "--port", "6380"}, redis.Cmd)
 	require.Equal(t, "node:20", job.Image)
+	require.Equal(t, "sleep", job.Entrypoint[0])
 	require.Equal(t, "--label ${{ github.job }}", job.WorkflowOptions)
 	require.Equal(t, "${{ vars.TITLE }}", job.Password)
 }