runtime: remove stale runtime check in tests

The check is not relevant anymore.
The comment claims that go run does not rebuild packages,
but this is not true. And we use go build anyway.
We may have added the check because without caching
rebuilding everything starting from runtime for each test
takes a while. But now we have caching.
So from every side this check just adds code and pain.

Change-Id: Ifbbb643724100622e5f9db884339b67cde4ba729
Reviewed-on: https://go-review.googlesource.com/c/go/+/202450
Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/crash_test.go

@@ -104,8 +104,6 @@ func buildTestProg(t *testing.T, binary string, flags ...string) (string, error)
 		t.Skip("-quick")
 	}
 
-	checkStaleRuntime(t)
-
 	testprog.Lock()
 	defer testprog.Unlock()
 	if testprog.dir == "" {
@@ -152,34 +150,6 @@ func TestVDSO(t *testing.T) {
 	}
 }
 
-var (
-	staleRuntimeOnce sync.Once // guards init of staleRuntimeErr
-	staleRuntimeErr  error
-)
-
-func checkStaleRuntime(t *testing.T) {
-	staleRuntimeOnce.Do(func() {
-		// 'go run' uses the installed copy of runtime.a, which may be out of date.
-		out, err := testenv.CleanCmdEnv(exec.Command(testenv.GoToolPath(t), "list", "-gcflags=all="+os.Getenv("GO_GCFLAGS"), "-f", "{{.Stale}}", "runtime")).CombinedOutput()
-		if err != nil {
-			staleRuntimeErr = fmt.Errorf("failed to execute 'go list': %v\n%v", err, string(out))
-			return
-		}
-		if string(out) != "false\n" {
-			t.Logf("go list -f {{.Stale}} runtime:\n%s", out)
-			out, err := testenv.CleanCmdEnv(exec.Command(testenv.GoToolPath(t), "list", "-gcflags=all="+os.Getenv("GO_GCFLAGS"), "-f", "{{.StaleReason}}", "runtime")).CombinedOutput()
-			if err != nil {
-				t.Logf("go list -f {{.StaleReason}} failed: %v", err)
-			}
-			t.Logf("go list -f {{.StaleReason}} runtime:\n%s", out)
-			staleRuntimeErr = fmt.Errorf("Stale runtime.a. Run 'go install runtime'.")
-		}
-	})
-	if staleRuntimeErr != nil {
-		t.Fatal(staleRuntimeErr)
-	}
-}
-
 func testCrashHandler(t *testing.T, cgo bool) {
 	type crashTest struct {
 		Cgo bool

src/runtime/crash_unix_test.go

@@ -78,8 +78,6 @@ func TestCrashDumpsAllThreads(t *testing.T) {
 
 	testenv.MustHaveGoBuild(t)
 
-	checkStaleRuntime(t)
-
 	t.Parallel()
 
 	dir, err := ioutil.TempDir("", "go-build")