Add a gyp flag to enable dcheck by default in release without

base/file_util_unittest.cc

Index: base/file_util_unittest.cc
===================================================================
--- base/file_util_unittest.cc	(revision 101967)
+++ base/file_util_unittest.cc	(working copy)
@@ -223,7 +223,7 @@
     EXPECT_EQ(value.result, result);
   }
 
-#ifdef NDEBUG
+#if defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON)
   file_util::AppendToPath(NULL, L"path");  // asserts in debug mode
 #endif
 }