gh-141671: Use __declspec(dllexport) when not building core

Author: encukou

Include/exports.h

@@ -26,7 +26,7 @@
 #endif
 
 #if defined(_WIN32) || defined(__CYGWIN__)
-    #if defined(Py_ENABLE_SHARED)
+    #if !defined(Py_BUILD_CORE) || defined(Py_ENABLE_SHARED)
         #define Py_IMPORTED_SYMBOL __declspec(dllimport)
         #define Py_EXPORTED_SYMBOL __declspec(dllexport)
         #define Py_LOCAL_SYMBOL