Fix preparing log file name.

src/base/platform/platform-posix.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Platform-specific code for POSIX goes here. This is not a platform on its
 // own, but contains the parts which are the same across the POSIX platforms
 // Linux, MacOS, FreeBSD, OpenBSD, NetBSD and QNX.
 
 #include <errno.h>
 #include <limits.h>
@@ skipping 338 matching lines @@
   fclose(file);
   return NULL;
 }
 
 
 bool OS::Remove(const char* path) {
   return (remove(path) == 0);
 }
 
 
+bool OS::isDirectorySeparator(const char ch) {
+  return ch == '/';
+}
+
+
 FILE* OS::OpenTemporaryFile() {
   return tmpfile();
 }
 
 
 const char* const OS::LogFileOpenMode = "w";
 
 
 void OS::Print(const char* format, ...) {
   va_list args;
@@ skipping 321 matching lines @@
 
 void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
   pthread_key_t pthread_key = LocalKeyToPthreadKey(key);
   int result = pthread_setspecific(pthread_key, value);
   DCHECK_EQ(0, result);
   USE(result);
 }
 
 
 } }  // namespace v8::base