[binutils-gdb] Don't pass -m64 to libcc1 on aarch64-linux.

[sergiodj+buildbot at sergiodj dot net]

*** TEST RESULTS FOR COMMIT 7045b1ca73b8c0cb12d1158f3bc59d251dca0fa5 ***

Author: Yao Qi <yao.qi@linaro.org>
Branch: master
Commit: 7045b1ca73b8c0cb12d1158f3bc59d251dca0fa5

Don't pass -m64 to libcc1 on aarch64-linux.

Nowadays, if we use "compile" on aarch64-linux, we'll get the following
error,

(gdb) compile code -- ;
aarch64-none-linux-gnu-gcc: error: unrecognized command line option '-m64'

because the default gcc_target_options returns "-m64" and
"-mcmodel=large", neither is useful to aarch64-linux.

gdb:

2018-01-17  Yao Qi  <yao.qi@linaro.org>

	* aarch64-linux-tdep.c (aarch64_linux_gcc_target_options): New
	function.
	(aarch64_linux_init_abi): Install it to gdbarch hook
	gcc_target_options.