flow_parser.js should not init a js_of_ocaml filesystem
flow_parser.js should not init a js_of_ocaml filesystem

Summary:
js_of_ocaml implements a pseudo filesystem. `flow_parser.js` doesn't read from files, so we should disable that.

this prevents js_of_ocaml from exporting some globals: `caml_create_file` and `caml_fs_tmp`

Fixes https://github.com/facebook/flow/issues/8609

Reviewed By: pieterv

Differential Revision: D26916968

fbshipit-source-id: a2661706fe135b2c0ca20b209951a738d6b9ec23

nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow,nmote/flow