fix(ci): invalid variables syntax

refs #604

.gitlab-ci.yml

@@ -99,7 +99,7 @@ build-dev:
     - schedules
     - web
   variables:
-    - BASEHREF=/cassiopee/$CI_COMMIT_REF_NAME/
+    - BASEHREF: "/cassiopee/$CI_COMMIT_REF_NAME/"
 
 build-prod:
   extends: .build
@@ -107,7 +107,7 @@ build-prod:
     - tags
     - devel
   variables:
-    - BASEHREF=/
+    - BASEHREF: "/"
 
 clean-stale-branches:
   stage: clean-stale-branches