Error if some files are ESM

[kuraga]

Minimal example:
rollup-issue2.zip, then node build.js.

Result:

Error: 'default' is not exported by another.js
    at error (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:3460:30)
    at Module.error (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:13358:9)
    at handleMissingExport (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:13048:21)
    at Module.traceVariable (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:13466:17)
    at ModuleScope.findVariable (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:12713:29)
    at Identifier$$1.bind (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:10111:40)
    at CallExpression.NodeBase.bind (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:9179:31)
    at CallExpression.bind (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:10224:31)
    at ExpressionStatement$$1.NodeBase.bind (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:9183:23)
    at Program.NodeBase.bind (/home/sasha/rollup_issue2/node_modules/rollup/dist/rollup.js:9179:31)

Note: see another.js.

We can have the same error without any "Node globals" such as process: just remove rollup-plugin-commonjs Rollup plugin from building and replace process by 'something'.

/cc @calvinmetcalf