internal/cpu: revise test to make it work properly with -cover

Fix up a test to insure that it does the right thing when
"go test -cover" is in effect.

Fixes #52761.

Change-Id: I0c141181e2dcaefd592fb04813f812f2800511da
Reviewed-on: https://go-review.googlesource.com/c/go/+/404715
Run-TryBot: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>

src/internal/cpu/cpu_test.go

@@ -10,7 +10,6 @@ import (
 	"internal/testenv"
 	"os"
 	"os/exec"
-	"strings"
 	"testing"
 )
 
@@ -35,13 +34,9 @@ func runDebugOptionsTest(t *testing.T, test string, options string) {
 	cmd.Env = append(cmd.Env, env)
 
 	output, err := cmd.CombinedOutput()
-	lines := strings.Fields(string(output))
-	lastline := lines[len(lines)-1]
-
-	got := strings.TrimSpace(lastline)
-	want := "PASS"
-	if err != nil || got != want {
-		t.Fatalf("%s with %s: want %s, got %v", test, env, want, got)
+	if err != nil {
+		t.Fatalf("%s with %s: run failed: %v output:\n%s\n",
+			test, env, err, string(output))
 	}
 }