scripts/xldd: better find sysroot with old gcc

Only starting with 4.4 does gcc have a -print-sysroot option.
For 4.3 or before, we have to play some tricks:
- ask gcc where libc.so is,
(we expect it in ${sysroot}/usr/lib/libc.so)
- trim /usr/lib/libc.so from the result

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@anciens.enib.fr>

# ia64 specific config options

# depends on EXPERIMENTAL

config ARCH_ia64

    select ARCH_SUPPORTS_64

    select ARCH_DEFAULT_64

    select ARCH_USE_MMU

    select ARCH_SUPPORTS_BOTH_ENDIAN

    help

      The ia64 architecture, as defined by:

        http://www.intel.com/design/itanium/arch_spec.htm