Improve dependencies in Gitlab CI

.gitlab-ci.yml

@@ -69,7 +69,7 @@ debian:
 
 centos:
   before_script:
-    - sudo dnf install m4-devel
+    - sudo dnf install m4
   stage: real
   image: ocaml/opam:centos
   script: "export OC_NOTEST=true; ./gitlab-ci.sh system"
@@ -77,13 +77,15 @@ centos:
 
 fedora:
   before_script:
-    - sudo dnf install m4-devel
+    - sudo dnf install m4
   stage: real
   image: ocaml/opam:fedora
   script: "export OC_NOTEST=true; ./gitlab-ci.sh system"
   allow_failure: true
 
 opensuse:
+  before_script:
+    - sudo zypper --non-interactive up && sudo zypper --non-interactive in m4
   stage: real
   image: ocaml/opam:opensuse
   script: "export OC_NOTEST=true; ./gitlab-ci.sh system"