Add a way to force the macos target in case it is set (mlc-ai#52)

Author: ykhrustalev

CMakeLists.txt

@@ -39,6 +39,11 @@ elseif (CMAKE_SYSTEM_NAME STREQUAL "Darwin")
   if (CMAKE_SYSTEM_PROCESSOR STREQUAL "arm64")
     set(TOKENIZERS_CPP_CARGO_TARGET aarch64-apple-darwin)
   endif()
+  if (CMAKE_OSX_DEPLOYMENT_TARGET)
+    set(CARGO_EXTRA_ENVS
+      MACOSX_DEPLOYMENT_TARGET=${CMAKE_OSX_DEPLOYMENT_TARGET}
+    )
+  endif()
 elseif (CMAKE_SYSTEM_NAME STREQUAL "Android")
   if (ANDROID_ABI STREQUAL "arm64-v8a")
     set(TOKENIZERS_CPP_CARGO_TARGET aarch64-linux-android)