make: Expose a 'linker_supports_icf' flag.

pylib/gyp/system_test.py

 #!/usr/bin/python
 
 # Copyright (c) 2011 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.
 
 import os
 import tempfile
 import shutil
 import subprocess
@@ skipping 39 matching lines @@
                       env={'ar': ar_command, 'cc': cc_command})
 
 
 def TestLinkerSupportsThreads(cc_command='cc'):
   """Test whether the linker supports the --threads flag."""
   return TestCommands(['%(cc)s -Wl,--threads test.c'],
                       files={'test.c': 'int main(){}'},
                       env={'cc': cc_command})
 
 
+def TestLinkerSupportsICF(cc_command='cc'):
+  """Test whether the linker supports identical code folding."""
+  return TestCommands(['%(cc)s -Wl,--icf=safe test.c'],
+                      files={'test.c': 'int main(){}'},
+                      env={'cc': cc_command})
+
+
 if __name__ == '__main__':
   # Run the various test functions and print the results.
   def RunTest(description, function, **kwargs):
     print "Testing " + description + ':',
     if function(**kwargs):
       print 'ok'
     else:
       print 'fail'
   RunTest("ar 'T' flag", TestArSupportsT)
   RunTest("ar 'T' flag with ccache", TestArSupportsT, cc_command='ccache cc')
   RunTest("ld --threads", TestLinkerSupportsThreads)