Clarified how ENV vars are merged.
Clarified how ENV vars are merged.

buildkite/agent,grosskur/agent,Jasperswaagman/agent,grosskur/agent,es/agent,Jasperswaagman/agent,es/agent,joelmoss/agent,Shopify/agent,joelmoss/agent,buildkite/agent,Shopify/agent,Jasperswaagman/agent,buildkite/agent,es/agent,grosskur/agent,Shopify/agent,joelmoss/agent