Xenomai user space tools fail to build for bfin target since it's
provide it's own pthread_atfork(), shm_open() and shm_unlink()
definition using the inline keyword and weak attribute.

With gcc 5+ the weak attribute is discarded by the inline keyword,
so each symbol are global and are redefined several time while
linking.

Fixes:
http://autobuild.buildroot.net/results/0c2/0c2e5eb4edd4f9427f61d3c9b67a12a7a0e24140Signed-off-by: Romain Naour <romain.naour@gmail.com>