Seems PR 11328 introduced a compiler warning:

In file included from ./Include/Python.h:64:0,
                 from ./Python/sysmodule.c:17:
./Python/sysmodule.c:1597:14: warning: ‘sys_clear_type_cache__doc__’ defined but not used [-Wunused-variable]
 PyDoc_STRVAR(sys_clear_type_cache__doc__,
              ^
./Include/pymacro.h:70:37: note: in definition of macro ‘PyDoc_VAR’
 #define PyDoc_VAR(name) static char name[]
                                     ^~~~
./Python/sysmodule.c:1597:1: note: in expansion of macro ‘PyDoc_STRVAR’
 PyDoc_STRVAR(sys_clear_type_cache__doc__,
 ^~~~~~~~~~~~