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)

 # Compute ARM-specific values

 CT_DoArchTupleValues() {

     # The architecture part of the tuple:

     CT_TARGET_ARCH="${CT_ARCH}${target_endian_eb}"

     # The system part of the tuple:

     case "${CT_LIBC},${CT_ARCH_ARM_EABI}" in

         *glibc,y)   CT_TARGET_SYS=gnueabi;;

         uClibc,y)   CT_TARGET_SYS=uclibcgnueabi;;

         none,y)     CT_TARGET_SYS=eabi;;

     esac

     # In case we're EABI, do *not* specify any ABI!

     # which means, either we do not have an ABI specified, or we're not EABI.

     CT_TestOrAbort "Internal error: CT_ARCH_ABI should not be set for EABI build." -z "${CT_ARCH_ABI}" -o -z "${CT_ARCH_ARM_EABI}"

 }