fix-regexp caused a 'assign to read only property' error

[RequireSun]

I use it in a weex project, and when i called string.prototype.split function in my code, it goes wrong with Cannot assign to read only property 'exec' of obj '[object RegExp]' error, here's the screenshot:

my project is pretty big, so i can't give a demo here.

it associates to the commit: Fix RegExp methods in old browsers #453

[RequireSun]

weex sometimes don't allow code to cover the native code, this code triggered the problem.

[RequireSun]

weex's instructions here:

Weex JS engine features support

[nicolo-ribaudo]

Core JS does a lot of monkey patching, I don't think that it can work with frozen builtins 🤔

[zloirock]

@RequireSun did it work with core-js@2.5.7?

[RequireSun]

@RequireSun did it work with core-js@2.5.7?

yes, i locked my dependency in 2.5.7

[nicolo-ribaudo]

We could use defineProperty instead of a normal assignment (unless Weex JS also makes everything non-configurable).