runtime: skip test that intermittently hangs on ppc64le

A new testcase TestSelectFairness was recently added, and
since then the ppc64le build tests have intermittently failed.

This adds a change to skip this test on ppc64le using
SkipFlaky to help determine if the problem is with the
test or something else with that commit.

Updates #22047

Change-Id: Idfef72ed791c5bd45c42ff180947fea3df280ea7
Reviewed-on: https://go-review.googlesource.com/67631
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/chan_test.go

@@ -5,6 +5,7 @@
 package runtime_test
 
 import (
+	"internal/testenv"
 	"math"
 	"runtime"
 	"sync"
@@ -433,6 +434,9 @@ func TestSelectStress(t *testing.T) {
 
 func TestSelectFairness(t *testing.T) {
 	const trials = 10000
+	if runtime.GOOS == "linux" && runtime.GOARCH == "ppc64le" {
+		testenv.SkipFlaky(t, 22047)
+	}
 	c1 := make(chan byte, trials+1)
 	c2 := make(chan byte, trials+1)
 	for i := 0; i < trials+1; i++ {