Add fix to support Summon/Linaro GCC ARM embedded toolchain.

Hi, would you please to review and merge it? Without this fix it produces unresolved _exit reference on ld stage. It happens due to summon/linaro gcc reports different signature on 'gcc --version'. Tested with:

rm-none-eabi-gcc (Linaro GCC 4.6-2011.10) 4.6.2 20111004 (prerelease)
Copyright (C) 2011 Free Software Foundation, Inc.

Thank you,
Dmitry