explain make parallelism

3 jobs for master in 5 minutes and 38 seconds (queued for 17 minutes and 7 seconds)
Status Job ID Name Coverage
  Build
passed #3699
fp-timing
build-coq8.6.1

00:02:45

passed #3698
fp-timing
build-coq8.7

00:02:39

 
  Opam
passed #3700
opam

00:00:13