Fix directory test on mac

runtime/bin/directory_test.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/directory.h"
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/isolate.h"
 #include "vm/thread.h"
 #include "vm/unit_test.h"
@@ skipping 52 matching lines @@
   EXPECT_NOTNULL(current);
 
   const char* system_temp = dart::bin::Directory::SystemTemp();
   EXPECT_NOTNULL(system_temp);
 
   EXPECT(dart::bin::Directory::SetCurrent(system_temp));
 
   const char* new_current = dart::bin::Directory::Current();
   EXPECT_NOTNULL(new_current);
 
-  EXPECT_EQ(0, strcmp(system_temp, new_current));
+  EXPECT_NOTNULL(strstr(new_current, system_temp));
 
   EXPECT(dart::bin::Directory::SetCurrent(current));
 }
 
 
 TEST_CASE(DirectoryCreateDelete) {
   const char* kTempDirName = "test_name";
 
   const char* system_temp = dart::bin::Directory::SystemTemp();
   EXPECT_NOTNULL(system_temp);
@@ skipping 50 matching lines @@
 
   r = dart::bin::Directory::Exists(name);
   EXPECT_EQ(dart::bin::Directory::DOES_NOT_EXIST, r);
 
   EXPECT(dart::bin::Directory::Delete(new_name, false));
   delete[] name;
   delete[] new_name;
 }
 
 }  // namespace dart