Build _ctypes_test as a shared module (fixes #721)

Author: geofft

cpython-unix/extension-modules.yml

@@ -145,6 +145,7 @@ _ctypes:
     - dl
 
 _ctypes_test:
+  build-mode: shared
   sources:
     - _ctypes/_ctypes_test.c
   links:

src/validation.rs

@@ -649,6 +649,10 @@ const _DEPENDENCY_PACKAGE_SYMBOLS_BUNDLED: &[&str] = &[
     "TkBindInit",
     "TkCreateFrame",
     "Tk_FreeGC",
+    // _ctypes_test module
+    "my_free",
+    "mystrdup",
+    "top",
 ];
 
 const PYTHON_EXPORTED_SYMBOLS: &[&str] = &[