Use a macro for the minimum supported version

Author: emmatyping

Modules/_zstd/_zstdmodule.c

@@ -308,7 +308,7 @@ _zstd__finalize_dict_impl(PyObject *module, PyBytesObject *custom_dict_bytes,
                           int compression_level)
 /*[clinic end generated code: output=9c2a7d8c845cee93 input=ef6f4f2b0b7e178d]*/
 {
-    if (ZSTD_versionNumber() < 10405) {
+    if (ZSTD_versionNumber() < PYTHON_MINIMUM_SUPPORTED_ZSTD_VERSION) {
         /* Must be dynamically linked */
         PyErr_Format(PyExc_NotImplementedError,
                 "The _finalize_dict function is only available when the underlying "

Modules/_zstd/_zstdmodule.h

@@ -16,7 +16,9 @@ Refactored for the CPython standard library by Emma Harper Smith.
 
 #include "pycore_lock.h" // PyMutex APIs
 
-#if ZSTD_VERSION_NUMBER < 10405
+#define PYTHON_MINIMUM_SUPPORTED_ZSTD_VERSION 10405
+
+#if ZSTD_VERSION_NUMBER < PYTHON_MINIMUM_SUPPORTED_ZSTD_VERSION
     #error "_zstd module requires zstd v1.4.5+"
 #endif