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6eb3e97d55
Remove Apple RNG fallbacks and simplify implementation Now that we have [higher Apple platform requirements](https://github.com/rust-lang/rust/pull/104385), the RNG code can be simplified a lot. Since `getentropy` still doesn't look to be usable outside macOS this implementation: - Removes any macOS fallback paths and unconditionally links to `getentropy` - Minimizes the implementation for everything else (iOS, watchOS, etc). `CCRandomGenerateBytes` was added in iOS 8 which means that we can use it now. It and `SecRandomCopyBytes` have the exact same functionality, but the former has a simpler API and no longer requires libstd to link to `Security.framework` for one function. Its also available in all the other target's SDKs. Why care about `getentropy` then though on macOS? Well, its still much more performant. Benchmarking shows it runs at ~2x the speed of `CCRandomGenerateBytes`, which makes sense since it directly pulls from the kernel vs going through its own generator etc. Semi-related to a previous, but reverted, attempt at improving this logic in https://github.com/rust-lang/rust/pull/101011