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

@@ -19,6 +19,12 @@ lint-dockerfile:
   script:
     - find . -name "Dockerfile" -execdir hadolint {} \;
 
+lint-shell-script:
+  stage: test
+  image: koalaman/shellcheck-alpine:latest
+  script:
+    - find . -name "*.sh" -exec shellcheck {} \;
+
 #
 # IMAGE BUILDS/PUSHES
 #
@@ -59,15 +65,6 @@ build-debian-jessie-build-dev:
   except:
     - master
 
-lint-debian-jessie-build-script:
-  stage: test
-  image: debian:latest
-  before_script:
-    - apt-get update
-    - apt-get install -y shellcheck
-  script:
-    - shellcheck ./debian/jessie/setup.sh
-
 # PHP 7.3
 build-php-7.3-master:
   stage: deploy