Build: Disable mmap fastmem for Apple Silicon

It uses 16K pages, which means we'd also have to protect at 16K
granularity... which might be okay, but there's probably going to be
more faults due to code/data in the same page, which negates much of the
benefit.

src/core/CMakeLists.txt

@@ -163,7 +163,11 @@ elseif(${CPU_ARCH} STREQUAL "aarch32")
   target_link_libraries(core PUBLIC vixl)
   message("Building AArch32 recompiler")
 elseif(${CPU_ARCH} STREQUAL "aarch64")
-  target_compile_definitions(core PUBLIC "WITH_RECOMPILER=1" "WITH_MMAP_FASTMEM=1")
+  target_compile_definitions(core PUBLIC "WITH_RECOMPILER=1")
+  if (NOT APPLE)
+    # Disabled until we support 16K pages.
+    target_compile_definitions(core PUBLIC "WITH_MMAP_FASTMEM=1")
+  endif()
   target_sources(core PRIVATE ${RECOMPILER_SRCS}
     cpu_recompiler_code_generator_aarch64.cpp
   )