runtime/pprof: continued attempt to deflake the VMInfo test.

This PR will use test.Skip to bypass a test run for which the vmmap
subprocess appears to hang before the test times out.
In addition it catches a different error message from vmmap that can
occur due to transient resource shortages and triggers a retry for
this additional case.

Fixes #62352

Change-Id: I3ae749e5cd78965c45b1b7c689b896493aa37ba0
Reviewed-on: https://go-review.googlesource.com/c/go/+/560935
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/pprof/vminfo_darwin_test.go

@@ -17,6 +17,7 @@ import (
 	"strconv"
 	"strings"
 	"testing"
+	"time"
 )
 
 func TestVMInfo(t *testing.T) {
@@ -56,18 +57,35 @@ func TestVMInfo(t *testing.T) {
 	}
 }
 
+type mapping struct {
+	hi, lo uint64
+	err    error
+}
+
 func useVMMapWithRetry(t *testing.T) (hi, lo uint64, err error) {
 	var retryable bool
+	ch := make(chan mapping)
+	go func() {
 		for {
 			hi, lo, retryable, err = useVMMap(t)
 			if err == nil {
-			return hi, lo, nil
+				ch <- mapping{hi, lo, nil}
+				return
 			}
 			if !retryable {
-			return 0, 0, err
+				ch <- mapping{0, 0, err}
+				return
 			}
 			t.Logf("retrying vmmap after error: %v", err)
 		}
+	}()
+	select {
+	case m := <-ch:
+		return m.hi, m.lo, m.err
+	case <-time.After(time.Minute):
+		t.Skip("vmmap taking too long")
+	}
+	return 0, 0, fmt.Errorf("unreachable")
 }
 
 func useVMMap(t *testing.T) (hi, lo uint64, retryable bool, err error) {