Pin build image to Alpine 3.15

.drone.yml

@@ -4,7 +4,7 @@ name: default
 
 steps:
 - name: build-release
-  image: alpine:latest
+  image: alpine:3.15
   environment:
     MIX_ENV: prod
   commands:
@@ -17,7 +17,7 @@ steps:
     - cd _build/prod/rel
     - tar czf "ha-handler-$(git describe --exact-match --tags $(git log -n1 --pretty='%h') || git rev-parse HEAD).tar.gz" ha_handler/
 - name: publish-release-archive
-  image: alpine:latest
+  image: alpine:3.15
   environment:
     LFTP_PASSWORD:
      from_secret: ssh_password