Modify ARM .S code so it can be processed by both gnu-as and llvm-mc.

pnacl/driver/pnacl-as.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.
 #
 
 import driver_tools
 
 env = driver_tools.env
 
 EXTRA_ENV = {
   'INPUTS'      : '',
   'OUTPUT'      : '',
 
   # Options
   'DIAGNOSTIC'  : '0',
   'ASPP_FLAGS': '-DNACL_LINUX=1',
 
   'AS_FLAGS_ARM'  : '-mfpu=vfp -march=armv7-a',
+  # BUG: http://code.google.com/p/nativeclient/issues/detail?id=1968
   # once we can use llvm's ARM assembler we should use these flags
   #'AS_FLAGS_ARM'   : '-assemble -filetype=obj -arch=arm -triple=armv7a-nacl',
   'AS_FLAGS_X8632' : '-assemble -filetype=obj -arch=x86 -triple=i686-nacl',
   'AS_FLAGS_X8664' : '-assemble -filetype=obj -arch=x86-64 -triple=x86_64-nacl',
 
   'RUN_BITCODE_AS' : '${LLVM_AS} ${input} -o ${output}',
   'RUN_NATIVE_AS' : '${AS_%ARCH%} ${AS_FLAGS_%ARCH%} ${input} -o ${output}',
 
   # NOTE: should we run the vanilla preprocessor instead?
   'RUN_PP' : '${CLANG} -E ${ASPP_FLAGS} ${input} -o ${output}'
@@ skipping 79 matching lines @@
     driver_tools.RunWithLog("${RUN_BITCODE_AS}")
   else:
     # .s to .o
     driver_tools.RunWithLog("${RUN_NATIVE_AS}")
   env.pop()
   return 0
 
 
 if __name__ == "__main__":
   driver_tools.DriverMain(main)