complibs/libelf: build with -fPIC

libelf is used by gcc to build the lto-plugin used
by binutils' gold to perform LTO.

This requires that files in libelf be compiled with
-fPIC to generate a proper .so.

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

 reporter_name="Remy Bohmer"

 reporter_url="linux@bohmer.net"

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