Created a buster ci environment

.gitlab-docker-armv7l.yml

@@ -1,6 +1,6 @@
 armv7l:build:
   variables:
-    VERSION: armv7l-stretch
+    VERSION: armv7l-buster
   stage: build
   image: docker:latest
   script:
@@ -13,4 +13,4 @@ armv7l:build:
   - docker
   - armv7l
   only:
-  - stretch
+  - buster

.gitlab-docker-x86_64.yml

@@ -1,6 +1,6 @@
 x86_64:build:
   variables:
-    VERSION: x86_64-stretch
+    VERSION: x86_64-buster
   stage: build
   image: docker:latest
   script:
@@ -13,4 +13,4 @@ x86_64:build:
   - docker
   - x86_64
   only:
-  - stretch
+  - buster

Dockerfile

@@ -1,7 +1,7 @@
 # NAME leenooks/ci-apt
-# VERSION stretch-slim
+# VERSION buster-slim
 
-FROM debian:stretch-slim
+FROM debian:buster-slim
 
 RUN apt-get update && apt-get install -y git \
 	build-essential devscripts debhelper dh-make quilt \