add opam descr

3 jobs for master in 3 minutes and 27 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #3260
fp-timing
stdpp-coq8.6

00:01:43

passed #3259
fp-timing
stdpp-coq8.6.1

00:01:40

passed #3258
fp-timing
stdpp-coq8.7

00:01:45