Update V8 to r6768 as required by WebKit r78450

Change-Id: Ib8868ff7147a76547a8d1d85f257ebe8546a3d3f
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index ab5c0a3..256dc75 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -122,6 +122,11 @@
 }
 
 
+bool OS::Remove(const char* path) {
+  return (remove(path) == 0);
+}
+
+
 const char* OS::LogFileOpenMode = "w";