runtime: remove canBackTrace variable from TestGdbPython

The canBackTrace variable is true for all of the architectures
Go supports and this is likely to remain the case as new
architectures are added.

Change-Id: I73900c018eb4b2e5c02fccd8d3e89853b2ba9d90
Reviewed-on: https://go-review.googlesource.com/22423Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/runtime/runtime-gdb_test.go

@@ -121,21 +121,11 @@ func TestGdbPython(t *testing.T) {
 		"-ex", "print strvar",
 		"-ex", "echo END\n",
 		"-ex", "down", // back to fmt.Println (goroutine 2 below only works at bottom of stack.  TODO: fix that)
+		"-ex", "echo BEGIN goroutine 2 bt\n",
+		"-ex", "goroutine 2 bt",
+		"-ex", "echo END\n",
+		filepath.Join(dir, "a.exe"),
 	}
-
-	// without framepointer, gdb cannot backtrace our non-standard
-	// stack frames on RISC architectures.
-	canBackTrace := false
-	switch runtime.GOARCH {
-	case "amd64", "386", "ppc64", "ppc64le", "arm", "arm64", "mips64", "mips64le", "s390x":
-		canBackTrace = true
-		args = append(args,
-			"-ex", "echo BEGIN goroutine 2 bt\n",
-			"-ex", "goroutine 2 bt",
-			"-ex", "echo END\n")
-	}
-
-	args = append(args, filepath.Join(dir, "a.exe"))
 	got, _ := exec.Command("gdb", args...).CombinedOutput()
 
 	firstLine := bytes.SplitN(got, []byte("\n"), 2)[0]
@@ -179,10 +169,8 @@ func TestGdbPython(t *testing.T) {
 	}
 
 	btGoroutineRe := regexp.MustCompile(`^#0\s+runtime.+at`)
-	if bl := blocks["goroutine 2 bt"]; canBackTrace && !btGoroutineRe.MatchString(bl) {
+	if bl := blocks["goroutine 2 bt"]; !btGoroutineRe.MatchString(bl) {
 		t.Fatalf("goroutine 2 bt failed: %s", bl)
-	} else if !canBackTrace {
-		t.Logf("gdb cannot backtrace for GOARCH=%s, skipped goroutine backtrace test", runtime.GOARCH)
 	}
 }