runtime/pprof: test for Darwin flake in TestVMInfo

If it contains
"No process corpse slots currently available, waiting to get one"
skip the test in short mode, so that run.bash works reliably
on developer laptops, but the flake is still recorded on builders.

The problem also seems to get better after a laptop reboot?

Updates #62352.

Change-Id: I12e8f594f0b830bacda5d8bfa594782345764c4a
Reviewed-on: https://go-review.googlesource.com/c/go/+/579295
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

src/runtime/pprof/vminfo_darwin_test.go

@@ -79,6 +79,9 @@ func useVMMap(t *testing.T) (hi, lo uint64, retryable bool, err error) {
 		t.Logf("vmmap output: %s", out)
 		if ee, ok := cmdErr.(*exec.ExitError); ok && len(ee.Stderr) > 0 {
 			t.Logf("%v: %v\n%s", cmd, cmdErr, ee.Stderr)
+			if testing.Short() && strings.Contains(string(ee.Stderr), "No process corpse slots currently available, waiting to get one") {
+				t.Skipf("Skipping knwn flake in short test mode")
+			}
 			retryable = bytes.Contains(ee.Stderr, []byte("resource shortage"))
 		}
 		t.Logf("%v: %v\n", cmd, cmdErr)