[test] Upgrade base OCaml to 4.08.1

Stronger linking restrictions were introduced in OCaml 4.08, I'd like
to have a look at what the impact is over the CI.

.gitlab-ci.yml

@@ -18,7 +18,7 @@ stages:
 variables:
   # Format: $IMAGE-V$DATE [Cache is not used as of today but kept here
   # for reference]
-  CACHEKEY: "bionic_coq-V2019-12-08-V82"
+  CACHEKEY: "bionic_coq-V2020-02-12-V72"
   IMAGE: "$CI_REGISTRY_IMAGE:$CACHEKEY"
   # By default, jobs run in the base switch; override to select another switch
   OPAM_SWITCH: "base"

dev/ci/docker/bionic_coq/Dockerfile

@@ -1,4 +1,4 @@
-# CACHEKEY: "bionic_coq-V2019-12-08-V82"
+# CACHEKEY: "bionic_coq-V2020-02-12-V72"
 # ^^ Update when modifying this file.
 
 FROM ubuntu:bionic
@@ -32,17 +32,17 @@ ENV NJOBS="2" \
     OPAMYES="true"
 
 # Base opam is the set of base packages required by Coq
-ENV COMPILER="4.05.0"
+ENV COMPILER="4.08.1"
 
 # Common OPAM packages.
 # `num` does not have a version number as the right version to install varies
 # with the compiler version.
-ENV BASE_OPAM="num ocamlfind.1.8.1 dune.2.0.0 ounit.2.0.8 odoc.1.4.2" \
+ENV BASE_OPAM="num ocamlfind.1.8.1 dune.2.1.3 ounit.2.2.2 odoc.1.4.2" \
     CI_OPAM="menhir.20190626 ocamlgraph.1.8.8" \
     BASE_ONLY_OPAM="elpi.1.8.0"
 
 # BASE switch; CI_OPAM contains Coq's CI dependencies.
-ENV COQIDE_OPAM="cairo2.0.6.1 lablgtk3-sourceview3.3.0.beta6"
+ENV COQIDE_OPAM="cairo2.0.6.1 lablgtk3-sourceview3.3.1.0"
 
 # Must add this to COQIDE_OPAM{,_EDGE} when we update the opam
 # packages "lablgtk3-gtksourceview3"
@@ -57,7 +57,7 @@ RUN opam switch create "${COMPILER}+32bit" && eval $(opam env) && \
 
 # EDGE switch
 ENV COMPILER_EDGE="4.09.0" \
-    COQIDE_OPAM_EDGE="cairo2.0.6.1 lablgtk3-sourceview3.3.0.beta6" \
+    COQIDE_OPAM_EDGE="cairo2.0.6.1 lablgtk3-sourceview3.3.1.0" \
     BASE_OPAM_EDGE="dune-release.1.3.3 ocamlformat.0.12"
 
 # EDGE+flambda switch, we install CI_OPAM as to be able to use