update Makefile

2 jobs for master in 11 minutes and 9 seconds (queued for 35 minutes and 57 seconds)
Status Job ID Name Coverage
  Build
passed #23164
fp
build-coq.8.8.2

00:06:11

failed #23163
fp
build-coq.dev

00:04:58

 
Name Stage Failure
failed
build-coq.dev Build
| - remove    coq-stdpp         dev.2018-11-08.2.df509b21
| - recompile coq dev
+-

The former state can be restored with:
opam switch import "/builds/iris/iron/opamroot/ocaml-base-compiler.4.07.0/.opam-switch/backup/state-20190201141513.export"
Or you can retry to install your package selection with:
opam install --restore
ERROR: Job failed: exit code 1