build: indicate the build byproducts for PythonKit (#1057)

Ensure that CMake is aware that the import library is a build byproduct
so that it knows how to wire up the dependencies.  This should repair
the Windows build.

Author: compnerd

CMakeLists.txt

@@ -95,6 +95,7 @@ if(ENABLE_PYTHON_SUPPORT)
         ${CMAKE_COMMAND} -E copy_if_different <BINARY_DIR>/swift/PythonKit.swiftdoc ${CMAKE_Swift_MODULE_DIRECTORY}/
     BUILD_BYPRODUCTS
       <BINARY_DIR>/PythonKit/${CMAKE_SHARED_LIBRARY_PREFIX}PythonKit${CMAKE_SHARED_LIBRARY_SUFFIX}
+      <BINARY_DIR>/PythonKit/${CMAKE_IMPORT_LIBRARY_PREFIX}PythonKit${CMAKE_IMPORT_LIBRARY_SUFFIX}
     UPDATE_DISCONNECTED
       TRUE
     STEP_TARGETS