Added support for two more (bfd) linker flags that will be useful

tools/llvm/driver/pnacl-ld.py

 #!/usr/bin/python
 # Copyright (c) 2011 The Native Client Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # IMPORTANT NOTE: If you make local mods to this file, you must run:
 #   %  tools/llvm/utman.sh driver
 # in order for them to take effect in the scons build.  This command
 # updates the copy in the toolchain/ tree.
 #
@@ skipping 133 matching lines @@
   ( ('(-Ttext)','(.*)'), "env.append('LD_FLAGS', $0, $1)"),
   ( ('(-Ttext=.*)'),     "env.append('LD_FLAGS', $0)"),
   ( ('-T', '(.*)'),    "env.set('LD_SCRIPT', $0)"),
 
   ( ('-e','(.*)'),     "env.append('LD_FLAGS', '-e', $0)"),
   ( ('(--section-start)','(.*)'), "env.append('LD_FLAGS', $0, $1)"),
   ( '(-?-soname=.*)',             "env.append('LD_FLAGS', $0)"),
   ( ('(-?-soname)', '(.*)'),      "env.append('LD_FLAGS', $0, $1)"),
   ( '(--eh-frame-hdr)',           "env.append('LD_FLAGS', $0)"),
 
+  ( '(--print-gc-sections)',      "env.append('LD_FLAGS', $0)"),
+  ( '(-gc-sections)',             "env.append('LD_FLAGS', $0)"),
+
   ( '-melf_nacl',          "env.set('ARCH', 'X8632')"),
   ( ('-m','elf_nacl'),     "env.set('ARCH', 'X8632')"),
   ( '-melf64_nacl',        "env.set('ARCH', 'X8664')"),
   ( ('-m','elf64_nacl'),   "env.set('ARCH', 'X8664')"),
   ( '-marmelf_nacl',       "env.set('ARCH', 'ARM')"),
   ( ('-m','armelf_nacl'),  "env.set('ARCH', 'ARM')"),
 
   ( ('-?-wrap', '(.+)'),    "env.append('WRAP_SYMBOLS', $0)"),
   ( ('-?-wrap=(.+)'),       "env.append('WRAP_SYMBOLS', $0)"),
 
@@ skipping 570 matching lines @@
     elif IsFlag(f):
       continue
     else:
       if not os.path.exists(f):
         Log.Fatal("Unable to open '%s'", f)
       ret.append(f)
   return ret
 
 if __name__ == "__main__":
   DriverMain(main)