Use MAC_OS_X_DEPLOYMENT_TARGET instead of rolling our own

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 have
-// been compiled with our SUPPORT_MACOSX_10_4 flag defined.
-// If SUPPORT_MACOSX_10_4 is not defined it just includes execinfo.h as normal,
-// otherwise it defines the symbols itself as weak linked imports, which enables
-// launching on 10.4 where they are not defined.
+
+// 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
 
-#ifdef SUPPORT_MACOSX_10_4
+#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 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
-
+#endif  // BASE_COMPAT_EXECINFO_H