use ocaml+flambda for most jobs

.gitlab-ci.yml

@@ -5,7 +5,7 @@ stages:
 
 variables:
   CPU_CORES: "10"
-  OCAML: "ocaml-base-compiler.4.14.0"
+  OCAML: "ocaml-variants.4.14.0+options ocaml-option-flambda"
 
 .only_branches: &only_branches
   only:
@@ -45,12 +45,12 @@ variables:
 build-coq.dev:
   <<: *template
   variables:
+    OCAML: "ocaml-base-compiler.4.14.0" # for faster rebuilds
     OPAM_PINS: "coq version dev"
 
 build-coq.8.18.0:
   <<: *template
   variables:
-    OCAML: "ocaml-variants.4.14.0+options ocaml-option-flambda"
     OPAM_PINS: "coq version 8.18.0"
     DENY_WARNINGS: "1"
     MANGLE_NAMES: "1"
@@ -71,7 +71,6 @@ build-coq.8.18.0-mr:
 trigger-iris.timing:
   <<: *template
   variables:
-    OCAML: "ocaml-variants.4.14.0+options ocaml-option-flambda"
     OPAM_PINS: "coq version 8.18.0   git+https://gitlab.mpi-sws.org/$IRIS_REPO#$IRIS_REV"
   tags:
   - fp-timing