Add Debian Jessie build image

This image is meant to be used to build packages for the Jessie release of Debian. See debian/nginx-build.

.gitlab-ci.yml

@@ -13,6 +13,7 @@ before_script:
 lint-dockerfile:
   stage: test
   image: hadolint/hadolint:latest-debian
+  services:
   before_script:
     - mkdir ~/.config
     - cp ./.hadolint.yaml ~/.config/hadolint.yaml
@@ -21,7 +22,8 @@ lint-dockerfile:
 
 lint-shell-script:
   stage: test
-  image: shellcheck:latest
+  services:
+  image: koalaman/shellcheck:latest
   script:
     - find . -name "*.sh" -execdir shellcheck {} \;