Migrate Python C extension to Cython (#3541)

python/CMakeLists.txt

@@ -0,0 +1,44 @@
+# NOTE: These must be checked before including Cython packages to ensure we are using the right python version.
+# Segfaults could happen if we are using the wrong version.
+set(PYTHON_INCLUDE_DIR ${PYTHON_INCLUDE_DIRS})
+
+# Find Cython executable
+get_filename_component(_python_path ${PYTHON_EXECUTABLE} PATH)
+find_program(CYTHON_EXECUTABLE
+  NAMES cython cython.bat cython3
+  HINTS ${_python_path})
+
+include(FindPackageHandleStandardArgs)
+FIND_PACKAGE_HANDLE_STANDARD_ARGS(Cython REQUIRED_VARS CYTHON_EXECUTABLE)
+
+include(UseCython)
+
+include_directories("${NUMPY_INCLUDE_DIR}")
+include_directories("${CMAKE_CURRENT_LIST_DIR}/../src")
+include_directories("${CMAKE_CURRENT_LIST_DIR}")
+
+# Include some generated Arrow headers.
+include_directories("${ARROW_SOURCE_DIR}/../arrow_ep-build/src")
+
+# If the pyx file is a C++ file, we should specify that here.
+set_source_files_properties(
+  ${CMAKE_CURRENT_LIST_DIR}/ray/_raylet.pyx
+  PROPERTIES CYTHON_IS_CXX TRUE)
+
+set(RAY_SRC_DIRECTORY "${CMAKE_CURRENT_LIST_DIR}/../src/ray")
+
+cython_add_module(
+  _raylet
+  ${RAY_SRC_DIRECTORY}/raylet/raylet_client.cc
+  ${CMAKE_CURRENT_LIST_DIR}/ray/_raylet.pyx)
+
+add_dependencies(_raylet ray_static)
+
+if(APPLE)
+    target_link_libraries(_raylet "-undefined dynamic_lookup" ray_static)
+else()
+    target_link_libraries(_raylet ray_static)
+endif()
+
+# Make sure that the Python extensions are built before copying the files.
+add_dependencies(copy_ray _raylet)