Perform build and magnum tuning

Building o//third_party/python now takes 5 seconds on my PC

This change works towards modifying Python to use runtime dispatching
when appropriate. For example, when loading the magnums in the socket
module, it's a good idea to check if the magnum is zero, because that
means the local system platform doesn't support it.

third_party/python/Modules/clinic/_weakref.inc

@@ -0,0 +1,63 @@
+/* clang-format off */
+/*[clinic input]
+preserve
+[clinic start generated code]*/
+
+PyDoc_STRVAR(_weakref_getweakrefcount__doc__,
+"getweakrefcount($module, object, /)\n"
+"--\n"
+"\n"
+"Return the number of weak references to \'object\'.");
+
+#define _WEAKREF_GETWEAKREFCOUNT_METHODDEF    \
+    {"getweakrefcount", (PyCFunction)_weakref_getweakrefcount, METH_O, _weakref_getweakrefcount__doc__},
+
+static Py_ssize_t
+_weakref_getweakrefcount_impl(PyObject *module, PyObject *object);
+
+static PyObject *
+_weakref_getweakrefcount(PyObject *module, PyObject *object)
+{
+    PyObject *return_value = NULL;
+    Py_ssize_t _return_value;
+
+    _return_value = _weakref_getweakrefcount_impl(module, object);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyLong_FromSsize_t(_return_value);
+
+exit:
+    return return_value;
+}
+
+PyDoc_STRVAR(_weakref__remove_dead_weakref__doc__,
+"_remove_dead_weakref($module, dct, key, /)\n"
+"--\n"
+"\n"
+"Atomically remove key from dict if it points to a dead weakref.");
+
+#define _WEAKREF__REMOVE_DEAD_WEAKREF_METHODDEF    \
+    {"_remove_dead_weakref", (PyCFunction)_weakref__remove_dead_weakref, METH_VARARGS, _weakref__remove_dead_weakref__doc__},
+
+static PyObject *
+_weakref__remove_dead_weakref_impl(PyObject *module, PyObject *dct,
+                                   PyObject *key);
+
+static PyObject *
+_weakref__remove_dead_weakref(PyObject *module, PyObject *args)
+{
+    PyObject *return_value = NULL;
+    PyObject *dct;
+    PyObject *key;
+
+    if (!PyArg_ParseTuple(args, "O!O:_remove_dead_weakref",
+        &PyDict_Type, &dct, &key)) {
+        goto exit;
+    }
+    return_value = _weakref__remove_dead_weakref_impl(module, dct, key);
+
+exit:
+    return return_value;
+}
+/*[clinic end generated code: output=e860dd818a44bc9b input=a9049054013a1b77]*/