Fix crash on iOS

[smilediver]

Describe your changes

This fixes the following crash on iOS: https://stackoverflow.com/questions/55361057/this-copy-of-libswiftcore-dylib-requires-an-os-version-prior-to-12-2-0

Issue ticket number and link

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  • I have checked readme and add important infos to this PR.
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[halx99]

why need /usr/lib/swift, axmol not use swift

[smilediver]

We use CocoaPods and some pods use Swift, for example Firebase. "/usr/lib/swift" is added by the pods xcconfig file to fix this issue, but CMAKE_INSTALL_RPATH set by Axmol sets this on the app target and inserts the "@executable_path/Frameworks" before the pod xcconfig overriding the value.