CI: Run smoke tests on docker images (#16441)

Updates `distribution-scripts` dependency to crystal-lang/distribution-scripts@b7af456

This includes the following changes:

* crystal-lang/distribution-scripts#392

Author: straight-shoota

.circleci/config.yml

@@ -8,7 +8,7 @@ parameters:
   distribution-scripts-version:
     description: "Git ref for version of https://github.com/crystal-lang/distribution-scripts/"
     type: string
-    default: "b6eef3f66ccb72a37026dcf306b37f1fc6da9de8"
+    default: "b7af456b433ebf114769ad8eb4f2c51c56c26189"
   previous_crystal_base_url:
     description: "Prefix for URLs to Crystal bootstrap compiler"
     type: string
@@ -354,6 +354,7 @@ jobs:
           source build.env
           cd docker
           make all64 TARBALLS=/tmp/workspace/build/
+          make smoke-all
       - persist_to_workspace:
           root: /tmp/workspace/distribution-scripts/docker/
           paths: