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>
(transplanted from aa2305c5b2a57fbcda9a1b5bb5fb3a476ac49a13)

# Overall toolchain configuration: paths, jobs, etc...

# Allow unconditional usage of tristates

config MODULES

    bool

    default y

menu "Paths and misc options"

source "config/global/ct-behave.in"

source "config/global/paths.in"

source "config/global/download.in"

source "config/global/extract.in"

source "config/global/build-behave.in"

source "config/global/logging.in"

endmenu