Merge branch 'jk/lsan-race-with-barrier'

CI jobs that run threaded programs under LSan has been giving false positives from time to time, which has been worked around. * jk/lsan-race-with-barrier: grep: work around LSan threading race with barrier index-pack: work around LSan threading race with barrier thread-utils: introduce optional barrier type Revert "index-pack: spawn threads atomically" test-lib: use individual lsan dir for --stress runs