runtime: print more information when testCgoPprof fails

Change-Id: I820dae0303959096f0c434b7e69ecb3bf070df09
Reviewed-on: https://go-review.googlesource.com/c/go/+/172197
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/crash_cgo_test.go

@@ -281,7 +281,7 @@ func testCgoPprof(t *testing.T, buildArg, runArg, top, bottom string) {
 			// See Issue 18243 and Issue 19938.
 			t.Skipf("Skipping failing test on Alpine (golang.org/issue/18243). Ignoring error: %v", err)
 		}
-		t.Fatal(err)
+		t.Fatalf("%s\n\n%v", got, err)
 	}
 	fn := strings.TrimSpace(string(got))
 	defer os.Remove(fn)