571964e1d Allow exported __const on iOS (flutter/engine#8217) (#29624)

https://github.com/flutter/engine/compare/e28fc3c810ee...571964e1d7b4

git log e28fc3c810ee3c62ad201bc49f4934f0ed20a82c..571964e1d7b49e5424c800b461006207d670736f --no-merges --oneline
571964e1d Allow exported __const on iOS (flutter/engine#8217)

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bin/internal/engine.version

-e28fc3c810ee3c62ad201bc49f4934f0ed20a82c
+571964e1d7b49e5424c800b461006207d670736f