Set ZERO_AR_DATE=1 when running libtool.

pylib/gyp/mac_tool.py

 #!/usr/bin/env python
 # Copyright (c) 2012 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Utility functions to perform Xcode-style build steps.
 
 These functions are executed via gyp-mac-tool when using the Makefile generator.
 """
 
@@ skipping 205 matching lines @@
     return subprocess.call(cmd_list)
 
   def ExecFilterLibtool(self, *cmd_list):
     """Calls libtool and filters out '/path/to/libtool: file: foo.o has no
     symbols'."""
     libtool_re = re.compile(r'^.*libtool: file: .* has no symbols$')
     libtool_re5 = re.compile(
         r'^.*libtool: warning for library: ' +
         r'.* the table of contents is empty ' +
         r'\(no object file members in the library define global symbols\)$')
-    libtoolout = subprocess.Popen(cmd_list, stderr=subprocess.PIPE)
+    env = os.environ.copy()
+    # Ref:
+    # http://www.opensource.apple.com/source/cctools/cctools-809/misc/libtool.c
+    # The problem with this flag is that it resets the file mtime on the file to
+    # epoch=0, e.g. 1970-1-1 or 1969-12-31 depending on daylight saving.
+    env['ZERO_AR_DATE'] = '1'
+    libtoolout = subprocess.Popen(cmd_list, stderr=subprocess.PIPE, env=env)
     _, err = libtoolout.communicate()
     for line in err.splitlines():
       if not libtool_re.match(line) and not libtool_re5.match(line):
         print >>sys.stderr, line
+    # Unconditionally touch any file .a file on the command line if present if
+    # succeeded. A bit hacky.
+    if not libtoolout.returncode:
+      archives = [
+        cmd for cmd in cmd_list if cmd.endswith('.a') and os.path.isfile(cmd)
+      ]
+      if len(archives) == 1:
+        os.utime(archives[0], None)
     return libtoolout.returncode
 
   def ExecPackageFramework(self, framework, version):
     """Takes a path to Something.framework and the Current version of that and
     sets up all the symlinks."""
     # Find the name of the binary based on the part before the ".framework".
     binary = os.path.basename(framework).split('.')[0]
 
     CURRENT = 'Current'
     RESOURCES = 'Resources'
@@ skipping 337 matching lines @@
         data = data.replace('$(%s)' % key, value)
       return data
     if isinstance(data, list):
       return [self._ExpandVariables(v, substitutions) for v in data]
     if isinstance(data, dict):
       return {k: self._ExpandVariables(data[k], substitutions) for k in data}
     return data
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))