XCode: Fix - Patch fmt consteval for Xcode 26/Clang compatibility

[cmgustavo]

Summary

Xcode 26 ships with a stricter version of Clang that rejects consteval in certain contexts inside the fmt library (v11.0.2). Specifically, fmt defines a macro called FMT_CONSTEVAL that resolves to the C++ consteval keyword when the compiler supports it — but Clang 26 raises an error when that keyword is used inside a lambda that returns a local struct, which is exactly what fmt's FMT_STRING macro does internally.

Fix

Added a post_install patch in the Podfile that rewrites #define FMT_CONSTEVAL consteval to #define FMT_CONSTEVAL constexpr in fmt/base.h after every pod install

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RN-2691