Move compat_execinfo to the mac directory since this is mac-specific....

base/compat_execinfo.h

-// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// A file you can include instead of <execinfo.h> if your project might need
-// to run on Mac OS X 10.4.
-
-#ifndef BASE_COMPAT_EXECINFO_H_
-#define BASE_COMPAT_EXECINFO_H_
-#pragma once
-
-#include "build/build_config.h"
-
-#if defined(OS_MACOSX)
-#include <AvailabilityMacros.h>
-#endif
-
-#if defined(OS_MACOSX) && MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_5
-// Manually define these here as weak imports, rather than including execinfo.h.
-// This lets us launch on 10.4 which does not have these calls.
-extern "C" {
-
-extern int backtrace(void**, int) __attribute__((weak_import));
-extern char** backtrace_symbols(void* const*, int)
-    __attribute__((weak_import));
-extern void backtrace_symbols_fd(void* const*, int, int)
-    __attribute__((weak_import));
-
-}  // extern "C"
-#else
-#include <execinfo.h>
-#endif
-
-#endif  // BASE_COMPAT_EXECINFO_H_