make start&length represent utf32 indices (macos) #4409

Job	Run time
Create test plan	4s
level1 / Haiku	1m 46s
level2 / PowerPC	1m 47s
level2 / Ubuntu 22.04 (Intel Compiler)	4m 13s
level2 / Sony PlayStation Vita (GLES w/ PVR_PSP2)	2m 51s
level2 / iOS (CMake & xcode)	2m 12s
level2 / Windows (MSVC, ARM)	4m 11s
level2 / tvOS (CMake & xcode)	2m 21s
level2 / Windows (MSVC, ARM64)	4m 17s
level2 / Android (CMake, lean)	2m 19s
level2 / Ubuntu 22.04	2m 33s
level2 / GDK (MSVC, x64)	2m 40s
level2 / Windows (MSVC, x86)	5m 56s
level2 / Nintendo 3DS	2m 6s
level2 / Windows (msys2, ucrt64)	4m 45s
level2 / MacOS (GNU prefix)	3m 13s
level2 / Ubuntu 22.04 (Intel oneAPI)	4m 48s
level2 / Emscripten	8m 32s
level2 / Windows (msys2, clang64)	4m 26s
level2 / Android (Android.mk)	1m 11s
level2 / Windows (msys2, clang32)	5m 8s
level2 / Android (Gradle)	2m 24s
level2 / Sony PlayStation Portable	3m 53s
level2 / MacOS (Framework) (x64)	7m 33s
level2 / Sony PlayStation Vita (GLES w/ pib)	2m 54s
level2 / Sony PlayStation 2	5m 3s
level2 / Windows (msys2, mingw64)	4m 27s
level2 / RISC OS	1m 21s
level2 / PowerPC64	1m 42s
level2 / Ubuntu 24.04 (ARM64)	5m 11s
level2 / Windows (msys2, mingw32)	5m 28s
level2 / FreeBSD	2m 49s
level2 / MacOS (Framework) (arm64)	2m 36s
level2 / Windows (MSVC, x64)	6m 11s
level2 / Windows (MSVC, clang-cl x86)	5m 59s
level2 / LoongArch64	1m 54s
level2 / NetBSD	3m 56s
level2 / Steam Linux Runtime (Sniper)	2m 53s
level2 / Windows (MSVC, clang-cl x64)	6m 35s
level2 / Android (CMake)	2m 39s
	2h 26m 47s

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