Environment variables containing a '.' cannot be set

At least one docker container requires configuration by setting envvars like foo.bar: "baz" in .gitlab-ci.yml, however, export fails to set these environment variables:

Here's an example failing build: https://gitlab.com/nick.thomas/gitlab-ee/builds/15155572

The variables section was:

variables:
  MYSQL_ALLOW_EMPTY_PASSWORD: "1"
  ELASTIC_URL: "http://elasticsearch:9200"
  RAILS_ENV: "test"
  NODE_ENV: "test"
  SIMPLECOV: "true"
  GIT_DEPTH: "20"
  PHANTOMJS_VERSION: "2.1.1"
  GET_SOURCES_ATTEMPTS: "3"
  KNAPSACK_RSPEC_SUITE_REPORT_PATH: knapsack/${CI_PROJECT_NAME}/rspec_report-master.json
  KNAPSACK_SPINACH_SUITE_REPORT_PATH: knapsack/${CI_PROJECT_NAME}/spinach_report-master.json
  # This hack is needed to make ES not that memory hungry
  ES_JAVA_OPTS: "-Xms256m -Xmx256m"
  indices.fielddata.cache.size: "20%"

(I've since discovered that we don't actually want to set this envvar, but there are plenty of others that we might want to use in the future)

added ~58730 executordocker labels

yml error can be fixed by quoting the key containing dots. "indices.fielddata.cache.size": "20%" but the error comes when the script is executed. Export does not allow dot in environment names. use env to fix it.