PolarFire SoC - C++ Exception Exits Before Catch

### Summary
On the PolarFire Icicle board, when building from `master` with a config based on `icicle:nsh` (plus config and flag changes detailed below), the cxxtest built-in app exception test fails. It throws the exception and then exits without catching the exception.

I've tried this on both the Icicle board and a PolarFire Renode simulation. I'm building with `riscv-none-elf-*` from xPack: `gcc version 13.2.0 (xPack GNU RISC-V Embedded GCC x86_64)`.

I'm hoping someone knows what the issue might be as I'm not familiar with the behind the scenes of exception handling. Meanwhile I'll keep working on this.

### Config
Changed optimization to `-Og` for debugging and set `-mstrict-align` to prevent a crash due to misaligned instructions.

Ran `make savedefconfig` and the following. The task size configs are set because I had to increase `CONFIG_DEFAULT_TASK_STACKSIZE` to prevent a stack overflow during exception unwinding.
```
$ diff boards/risc-v/mpfs/icicle/configs/nsh/defconfig defconfig
9a10,12
> # CONFIG_NSH_DISABLE_MB is not set
> # CONFIG_NSH_DISABLE_MH is not set
> # CONFIG_NSH_DISABLE_MW is not set
21a25,26
> CONFIG_CXX_EXCEPTION=y
> CONFIG_CXX_RTTI=y
25a31
> CONFIG_DEFAULT_TASK_STACKSIZE=32768
30a37
> CONFIG_HAVE_CXX=y
34a42,43
> CONFIG_LIBCXX=y
> CONFIG_LIBCXXABI=y
37a47
> CONFIG_LIBM=y
50a61
> CONFIG_POSIX_SPAWN_DEFAULT_STACKSIZE=2048
51a63
> CONFIG_PTHREAD_STACK_DEFAULT=2048
58a71
> CONFIG_SCHED_HPWORKSTACKSIZE=2048
59a73
> CONFIG_SCHED_LPWORKSTACKSIZE=2048
66a81
> CONFIG_SYSTEM_NSH_STACKSIZE=2048
68a84
> CONFIG_TESTING_CXXTEST=y
69a86
> CONFIG_TESTING_GETPRIME_STACKSIZE=2048
70a88,89
> CONFIG_TESTING_OSTEST_FPUSTACKSIZE=2048
> CONFIG_TLS_NELEM=4
```