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>
(transplanted from c48aba92cbeb7b7dce956a63ec65d3296735cc16)

 --- binutils/ld/ldmain.c

 +++ binutils/ld/ldmain.c

 @@ -296,6 +296,7 @@ main (int argc, char **argv)

    link_info.allow_undefined_version = TRUE;

    link_info.keep_memory = TRUE;

 +  link_info.new_dtags = TRUE;

    link_info.combreloc = TRUE;

    link_info.strip_discarded = TRUE;

    link_info.callbacks = &link_callbacks;