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

@@ -25,7 +25,7 @@ lint-shell-script:
   services:
   image: koalaman/shellcheck:latest
   script:
-    - find . -name "*.sh" -execdir shellcheck {} \;
+    - find . -name "*.sh" -exec shellcheck {} \;
 
 #
 # IMAGE BUILDS/PUSHES