Fix resolving @babel/runtime for external modules (#6837)
Fix resolving @babel/runtime for external modules (#6837)

See https://github.com/gatsbyjs/gatsby/issues/6030#issuecomment-405624139 for further details
ChristopherBiscardi/gatsby,gatsbyjs/gatsby,mingaldrichgan/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,0x80/gatsby,gatsbyjs/gatsby,0x80/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby,mingaldrichgan/gatsby,0x80/gatsby,mingaldrichgan/gatsby,gatsbyjs/gatsby,ChristopherBiscardi/gatsby,gatsbyjs/gatsby