Extern declare protobuf_globals (#6946)

php/ext/google/protobuf/protobuf.c

@@ -39,6 +39,8 @@ static PHP_RSHUTDOWN_FUNCTION(protobuf);
 static PHP_MINIT_FUNCTION(protobuf);
 static PHP_MSHUTDOWN_FUNCTION(protobuf);
 
+ZEND_DECLARE_MODULE_GLOBALS(protobuf)
+
 // Global map from upb {msg,enum}defs to wrapper Descriptor/EnumDescriptor
 // instances.
 static HashTable* upb_def_to_php_obj_map;

php/ext/google/protobuf/protobuf.h

@@ -689,7 +689,7 @@ ZEND_BEGIN_MODULE_GLOBALS(protobuf)
   zend_bool keep_descriptor_pool_after_request;
 ZEND_END_MODULE_GLOBALS(protobuf)
 
-ZEND_DECLARE_MODULE_GLOBALS(protobuf)
+ZEND_EXTERN_MODULE_GLOBALS(protobuf)
 
 #ifdef ZTS
 #define PROTOBUF_G(v) TSRMG(protobuf_globals_id, zend_protobuf_globals *, v)