No core file generated for division by zero

```
# make
g++ -g -MMD -MP -c -o main.o main.cpp
main.cpp: In function 'int f()':
main.cpp:5:12: warning: division by zero [-Wdiv-by-zero]
5 | int n = 1 / 0;
| ~~^~~
g++ main.o -o main
#
# ulimit -c
unlimited
#
# ./main
hello
#
# cat main.cpp
#include
using namespace std;

int f() {
int n = 1 / 0;
}

int main() {
cout << "hello\n";
f();
}
#
```

Start with the provided main.cpp reproducer and run make, then execute ./main with ulimit -c set to unlimited. Investigate why the division-by-zero case does not produce a core file; done means the reproducer generates the expected core file under the shown conditions.

Written by the indexing model from the issue text.