of this is to not have to link against -lrt because that causes
a different back-trace on certain x86 and s390x environments.
See the thread with subject
"helgrind/tests/cond_timedwait_invalid failing on x86"
on valgrind-developers for more details.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12246