win: symbol exports and minor fixes (#3024)

Co-authored-by: Cheng <[email protected]>

benchmarks/cpp/CMakeLists.txt

@@ -3,6 +3,14 @@ function(build_benchmark SRCFILE)
   set(target "${src_name}")
   add_executable(${target} ${SRCFILE})
   target_link_libraries(${target} PRIVATE mlx)
+  # On Windows, copy the mlx DLL to the executable directory for runtime loading
+  if(WIN32 AND BUILD_SHARED_LIBS)
+    add_custom_command(
+      TARGET ${target}
+      POST_BUILD
+      COMMAND ${CMAKE_COMMAND} -E copy_if_different $<TARGET_FILE:mlx>
+              $<TARGET_FILE_DIR:${target}>)
+  endif()
 endfunction(build_benchmark)
 
 build_benchmark(single_ops.cpp)