gh-151422: Don't link libffi into _ctypes_test.so

Minor build fix

Author: hoodmane

configure

@@ -8447,9 +8447,11 @@ PY_STDLIB_MOD([_testmultiphase], [test "$TEST_MODULES" = yes], [test "$ac_cv_fun
 PY_STDLIB_MOD([_testsinglephase], [test "$TEST_MODULES" = yes], [test "$ac_cv_func_dlopen" = yes])
 PY_STDLIB_MOD([xxsubtype], [test "$TEST_MODULES" = yes])
 PY_STDLIB_MOD([_xxtestfuzz], [test "$TEST_MODULES" = yes])
+dnl Check have_libffi so _ctypes_test is only built if _ctypes is built.
+dnl _ctypes_test doesn't use libffi directly.
 PY_STDLIB_MOD([_ctypes_test],
   [test "$TEST_MODULES" = yes], [test "$have_libffi" = yes -a "$ac_cv_func_dlopen" = yes],
-  [$LIBFFI_CFLAGS], [$LIBFFI_LIBS $LIBM])
+  [], [$LIBM])
 
 dnl Limited API template modules.
 dnl Emscripten does not support shared libraries yet.