Instead of calling setup_sage_signal_handler() from stdsage.c, call it instead from Cython when importing sage.ext.interrupt (renamed from sage.ext.c_lib).

This also bypasses the initialization of the global_empty_tuple from stdsage.c, but that is no longer used since #17668.

Component: c_lib

Author: Jeroen Demeyer

Branch/Commit: 1d41ca2

Reviewer: Marc Mezzarobba

Issue created by migration from https://trac.sagemath.org/ticket/17900