tests/cli/harness: use unused Verbose flag to pipe daemon outputs

I did this to be able to obtain actual daemon output on the screen while
debugging tests. Might be useful in the future even though it needs to
manually set verbose somewhere.

test/cli/harness/run.go

@@ -3,6 +3,7 @@ package harness
 import (
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
 	"strings"
 )
@@ -60,8 +61,27 @@ func environToMap(environ []string) map[string]string {
 
 func (r *Runner) Run(req RunRequest) *RunResult {
 	cmd := exec.Command(req.Path, req.Args...)
-	stdout := &Buffer{}
-	stderr := &Buffer{}
+	var stdout io.Writer
+	var stderr io.Writer
+	outbuf := &Buffer{}
+	errbuf := &Buffer{}
+
+	if r.Verbose {
+		or, ow := io.Pipe()
+		errr, errw := io.Pipe()
+		stdout = io.MultiWriter(outbuf, ow)
+		stderr = io.MultiWriter(errbuf, errw)
+		go func() {
+			_, _ = io.Copy(os.Stdout, or)
+		}()
+		go func() {
+			_, _ = io.Copy(os.Stderr, errr)
+		}()
+	} else {
+		stdout = outbuf
+		stderr = errbuf
+	}
+
 	cmd.Stdout = stdout
 	cmd.Stderr = stderr
 	cmd.Dir = r.Dir
@@ -83,8 +103,8 @@ func (r *Runner) Run(req RunRequest) *RunResult {
 	err := req.RunFunc(cmd)
 
 	result := RunResult{
-		Stdout: stdout,
-		Stderr: stderr,
+		Stdout: outbuf,
+		Stderr: errbuf,
 		Cmd:    cmd,
 		Err:    err,
 	}