bump ocaml version

3 jobs for master in 2 minutes and 7 seconds (queued for 4 seconds)
Name Stage Failure
failed
build-coq.8.13.2 Build
  - you won't be able to use mercurial repositories unless you install the hg command on your system.
- you won't be able to use darcs repositories unless you install the darcs command on your system.


<><> Fetching repository information ><><><><><><><><><><><><><><><><><><><><><>
[default] Initialised
[ERROR] No compiler matching 'ocaml-base-compiler.4.13.2' found, use 'opam switch list-available' to see what is available, or use '--packages' to select packages explicitly.
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

failed
build-coq.8.14.1 Build
  - you won't be able to use mercurial repositories unless you install the hg command on your system.
- you won't be able to use darcs repositories unless you install the darcs command on your system.


<><> Fetching repository information ><><><><><><><><><><><><><><><><><><><><><>
[default] Initialised
[ERROR] No compiler matching 'ocaml-base-compiler.4.13.2' found, use 'opam switch list-available' to see what is available, or use '--packages' to select packages explicitly.
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1

failed
build-coq.8.15.0 Build
  - you won't be able to use mercurial repositories unless you install the hg command on your system.
- you won't be able to use darcs repositories unless you install the darcs command on your system.


<><> Fetching repository information ><><><><><><><><><><><><><><><><><><><><><>
[default] Initialised
[ERROR] No compiler matching 'ocaml-base-compiler.4.13.2' found, use 'opam switch list-available' to see what is available, or use '--packages' to select packages explicitly.
Cleaning up project directory and file based variables
ERROR: Job failed: exit code 1