glibc moved clock_* functions from librt to the core libc. As a result,
clock_gettime is no more a suitable symbol to use when finding librt.
Look for mq_open instead.
Reference:
http://www.sourceware.org/git/gitweb.cgi?p=glibc.git&h=6e6249d0b461b952d0f544792372663feb6d792a