Fix call set_info_plist_value resulting in bplist file

[sainttail]

Refer to #6810

Since, I'm not too familiar with ruby and this issue happens on some specific machines (which happens to be me). So I try to fix it.

This PR seem like it solve that problem but I don't know why. Can someone explain this to me?

Thanks.

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[mfurtak]

I can confirm that this change fixes things relative to your sample project that exhibits the problem.

The two calls should be equivalent, so I think this change is fine. The fact that they're resulting in different outcomes is confounding 😫