feat: add Metal INT8 ConvRot support (#2297)

CMakeLists.txt

@@ -111,6 +111,12 @@ if(SD_CUDA)
 endif()
 
 if(SD_METAL)
+    if(NOT SD_USE_UPSTREAM_GGML)
+        if(CMAKE_VERSION VERSION_LESS 3.16)
+            message(FATAL_ERROR "SD_METAL with SD_USE_UPSTREAM_GGML=OFF requires CMake 3.16 or later for OBJC and OBJCXX support")
+        endif()
+        enable_language(OBJC OBJCXX)
+    endif()
     message("-- Use Metal as backend stable-diffusion")
     set(GGML_METAL ON)
 endif()
@@ -364,6 +370,11 @@ if (SD_CUDA)
     endif()
 endif()
 set(SD_BACKEND_REGISTRATIONS)
+if (SD_METAL AND NOT SD_USE_UPSTREAM_GGML)
+    add_subdirectory(src/core/metal)
+    target_link_libraries(${SD_LIB} PRIVATE "-framework Foundation" "-framework Metal")
+    list(APPEND SD_BACKEND_REGISTRATIONS sd_ggml_register_metal_i8)
+endif()
 if (NOT SD_USE_UPSTREAM_GGML AND (SD_CUDA OR SD_HIPBLAS OR SD_MUSA))
     if(SD_HIPBLAS)
         include(cmake/hip.cmake)