libc/uClibc: fix building on system with recent glibc

While trying to build a toolchain with ct-ng 1.5.0,
arm-unknown-linux-uclibcgnueabi target,
I get the following error:

[INFO ] Installing C library headers
[EXTRA] Copying sources to build dir
[EXTRA] Applying configuration
[EXTRA] Building headers
[EXTRA] Installing headers
[ERROR] extra/scripts/unifdef.c:209: error: conflicting types for 'getline'
[ERROR] make[2]: *** [extra/scripts/unifdef] Error 1
[ERROR] Build failed in step 'Installing C library headers'

The following patch solves the problem.
(It's a backport of this uClibc commit:
http://git.uclibc.org/uClibc/commit/?id=49e81cada73616864b9b31df0aeb6961c30f5a6e
)

[--SNIP from another mail--]
AFAIK this is a problem since glibc 2.10.
(transplanted from 1ba79f2126df8bd89120899a58f2d0bcc2e9c771)

 (C) 2007 Yann E. MORIN <yann.morin.1998@anciens.enib.fr>

 License: LGPL v2.1

 Shut off a stupid warning: preffered-stack-boundary must be between 4 ad 12,

 and 2 is not.

 diff -dur glibc-2.5.orig/sysdeps/i386/Makefile glibc-2.5/sysdeps/i386/Makefile

 --- glibc-2.5.orig/sysdeps/i386/Makefile	2005-03-06 01:18:16.000000000 +0100

 +++ glibc-2.5/sysdeps/i386/Makefile	2007-05-27 17:49:37.000000000 +0200

 @@ -36,7 +36,7 @@

  ifeq ($(subdir),csu)

  sysdep-CFLAGS += -mpreferred-stack-boundary=4

  else

 -sysdep-CFLAGS += -mpreferred-stack-boundary=2

 +sysdep-CFLAGS += -mpreferred-stack-boundary=4

  # Likewise, any function which calls user callbacks

  uses-callbacks += -mpreferred-stack-boundary=4

  # Likewise, any stack alignment tests