Rollup merge of #130132 - sunshowers:illumos-sigsegv, r=Noratrieb

[illumos] enable SIGSEGV handler to detect stack overflows

Use the same code as Solaris. I couldn't find any tests regarding this, but I did test a stage0 build against my stack-exhaust-test binary [1]. Before:

```
running with use_stacker = No, new_thread = false, make_large_local = false
zsh: segmentation fault (core dumped)  cargo run
```

After:

```
running with use_stacker = No, new_thread = false, make_large_local = false

thread 'main' has overflowed its stack
fatal runtime error: stack overflow
zsh: IOT instruction (core dumped)  cargo +stage0 run
```

Fixes #128568.

[1] https://github.com/sunshowers/stack-exhaust-test/

Author: workingjubilee