lang/quickjs: update to 2020-04-12

Changes since 2020-01-19:

2020-04-12:

- added cross realm support
- added AggregateError and Promise.any
- added env, uid and gid options in os.exec()
- misc bug fixes

2020-03-16:

- reworked error handling in std and os libraries: suppressed I/O
  exceptions in std FILE functions and return a positive errno value
  when it is explicit
- output exception messages to stderr
- added std.loadFile(), std.strerror(), std.FILE.prototype.tello()
- added JS_GetRuntimeOpaque(), JS_SetRuntimeOpaque(), JS_NewUint32()
- updated to Unicode 13.0.0
- misc bug fixes

(rillig)