fix child_process.exec options format

[dinuchiriac]

The env should be a property of an options Object and should not be passed directly. By sending it directly it will clash with other libraries that are trying to override exec Options. In my case, this is pkg library, see: https://github.com/zeit/pkg/blob/master/prelude/bootstrap.js#L1336
See child_process.exec docs: https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback

[friedrith]

Thx for the PR, I resolve conflicts and I merge it after.

[lock]

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