runtime: fix TestAbort on non-x86 arches

CL 122515 tightened TestAbort to look for breakpoint exceptions and
not just general signal crashes, but this only applies on x86 arches.
On non-x86 arches we use a nil pointer dereference to abort, so the
test is now failing.

This CL re-loosens TestAbort on non-x86 arches to only expect a signal
traceback.

Should fix the build on linux/arm, linux/arm64, linux/ppc64, and
linux/s390x.

Change-Id: I1065341180ab5ab4da63b406c641dcde93c9490b
Reviewed-on: https://go-review.googlesource.com/122580
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/crash_test.go

@@ -648,13 +648,19 @@ func TestAbort(t *testing.T) {
 	if strings.Contains(output, "BAD") {
 		t.Errorf("output contains BAD:\n%s", output)
 	}
-	// Check that it's a breakpoint traceback.
-	want := "SIGTRAP"
-	switch runtime.GOOS {
-	case "plan9":
-		want = "sys: breakpoint"
-	case "windows":
-		want = "Exception 0x80000003"
+	// Check that it's a signal traceback.
+	want := "PC="
+	// For systems that use a breakpoint, check specifically for that.
+	switch runtime.GOARCH {
+	case "386", "amd64":
+		switch runtime.GOOS {
+		case "plan9":
+			want = "sys: breakpoint"
+		case "windows":
+			want = "Exception 0x80000003"
+		default:
+			want = "SIGTRAP"
+		}
 	}
 	if !strings.Contains(output, want) {
 		t.Errorf("output does not contain %q:\n%s", want, output)