Handle fancy_abort before diagnostic initialization [PR98586]

Handle fancy_abort before diagnostic initialization [PR98586]

If fancy_abort is called before the diagnostic subsystem is initialized,
internal_error will crash internally in a way that prevents a useful
message reaching the user.

This can happen with libgccjit in the case of gcc_assert failures
that occur outside of the libgccjit mutex that guards the rest of
gcc's state, including global_dc (when global_dc may not be
initialized yet, or might be in use by another thread).

I tried a few approaches to fixing this as noted in PR jit/98586
e.g. using a temporary diagnostic_context and initializing it for
the call to internal_error, however the more code that runs, the
more chance there is for other errors to occur.

The best fix appears to be to simply fall back to a minimal abort
implementation that only relies on i18n, as implemented by this
patch.

gcc/ChangeLog:
	PR jit/98586
	* diagnostic.c (diagnostic_kind_text): Break out this array
	from...
	(diagnostic_build_prefix): ...here.
	(fancy_abort): Detect when diagnostic_initialize has not yet been
	called and fall back to a minimal implementation of printing the
	ICE, rather than segfaulting in internal_error.