Fix missing docker experimental env

Sh4d1 · web-flow · commit e8dc46a5df16 · 2019-11-11T23:45:53.000+01:00
diff --git a/cloudbuild.yaml b/cloudbuild.yaml
@@ -7,6 +7,7 @@ steps:
     env:
     - TAG=$_GIT_TAG
     - BASE_REF=$_PULL_BASE_REF
+    - DOCKER_CLI_EXPERIMENTAL=enabled
     args:
     - release-staging
 substitutions:
