complibs/libelf: use target ranlib

For portability, the right ranlib for the target must be passed to
libelf's configure.

Signed-off-by: "Titus von Boxberg" <titus@v9g.de>

reporter_name="Remy Bohmer"

reporter_url="linux@bohmer.net"

reporter_comment="Example for building a toolchain for m68000 bare metal targets"