runtime: re-enable crash test on FreeBSD

It also passes on FreeBSD.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/6812103

src/pkg/runtime/crash_test.go

@@ -9,7 +9,6 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
-	"runtime"
 	"testing"
 	"text/template"
 )
@@ -22,12 +21,6 @@ type crashTest struct {
 // both main (m0) and non-main threads (m).
 
 func testCrashHandler(t *testing.T, ct *crashTest) {
-	if runtime.GOOS == "freebsd" {
-		// TODO(brainman): do not know why this test fails on freebsd
-		t.Logf("skipping test on %q", runtime.GOOS)
-		return
-	}
-
 	st := template.Must(template.New("crashSource").Parse(crashSource))
 
 	dir, err := ioutil.TempDir("", "go-build")