macOS compiles the existing POSIX/Linux code paths (KYTY_PLATFORM_LINUX)
targeting x86_64 under Rosetta 2. Adds an APPLE branch to the build:
selects Apple's ld64 linker, unsets the Ninja response-file forcing (Apple
ar has no @file support), derives the target arch from CMAKE_OSX_ARCHITECTURES
for cpuinfo/ffmpeg, and re-signs the binary post-build with JIT entitlements
(required to execute written trampolines and Rosetta-translated guest code).
All changes are guarded by if(APPLE); Windows and Linux configuration is
unchanged.
(cherry picked from commit 13be13b757)
