Don't add stack_chk_fail_local.o to libc.a [BZ #21740]

commit 524a8ef2
Author: Nick Alcock <nick.alcock@oracle.com>
Date:   Mon Dec 26 10:08:57 2016 +0100

    PLT avoidance for __stack_chk_fail [BZ #7065]

    Add a hidden __stack_chk_fail_local alias to libc.so,
    and make sure that on targets which use __stack_chk_fail,
    this does not introduce a local PLT reference into libc.so.

which unconditionally added

strong_alias (__stack_chk_fail, __stack_chk_fail_local)

defines __stack_chk_fail_local as an alias of __stack_chk_fail in libc.a.
There is no need to add stack_chk_fail_local.o to libc.a.  We only need
to add stack_chk_fail_local.oS to libc_nonshared.a.

Tested on x86-64:

[hjl@gnu-skl-1 build-x86_64-linux]$ nm libc.a | grep __stack_chk_fail
0000000000000000 T __stack_chk_fail
0000000000000000 T __stack_chk_fail_local
[hjl@gnu-skl-1 build-x86_64-linux]$ nm libc_nonshared.a | grep __stack_chk_fail_local
0000000000000000 T __stack_chk_fail_local
[hjl@gnu-skl-1 build-x86_64-linux]$

	[BZ #21740]
	* debug/Makefile (elide-routines.o): New.