Attempt to fix build error

Related to golang/go#40893

The command "npm run export" generates an error, because it uses the
unimplemented syscall "copyfile". This commit attempts to pin Docker
version.

.circleci/config.yml

@@ -6,7 +6,8 @@ jobs:
       - image: circleci/buildpack-deps:stretch
     steps:
       - checkout
-      - setup_remote_docker
+      - setup_remote_docker:
+          version: 18.09.3
       - run:
           name: Build docker image
           command: |