Change lookup path for Dart native extensions shared libraries.

runtime/bin/extensions.h

Index: runtime/bin/extensions.h
diff --git a/runtime/bin/extensions.h b/runtime/bin/extensions.h
index b62c7637afc1e18b8809311142cd527b99cee0e5..a233a25e5c01326d0f0c4c1d61e04dd3190dfc99 100644
--- a/runtime/bin/extensions.h
+++ b/runtime/bin/extensions.h
@@ -20,7 +20,8 @@ class Extensions {
   static char* Concatenate(const char** strings);
 
   // Platform-specific implementations.
-  static void* LoadExtensionLibrary(const char* library_name);
+  static void* LoadExtensionLibrary(const char* library_path,
+                                    const char* extension_name);
   static void* ResolveSymbol(void* lib_handle, const char* symbol);
 
   DISALLOW_ALLOCATION();