elfutils: fix sparc64 build, -fPIC required

Fixes following autobuild errors:
http://autobuild.buildroot.net/results/82cc7766d2c805146e94baf82a24d1002f56593d/
http://autobuild.buildroot.net/results/ca4ca362581ee0111cba389d1afbff287692c21b/



Signed-off-by: Waldemar Brodkorb <wbx@openadk.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>