Mark M2_flint_abort as FLINT_NORETURN

[d-torrance]

Otherwise, compilation can fail w/:

../../../../Macaulay2/d/main.cpp:92:3: fatal error: no matching function for call to 'flint_set_abort'
   92 |   flint_set_abort(M2_flint_abort);
      |   ^~~~~~~~~~~~~~~
/usr/include/flint/flint.h:222:6: note: candidate function not viable: no known conversion from 'void ()' to 'void (*)() __attribute__((noreturn))' for 1st argument
  222 | void flint_set_abort(FLINT_NORETURN void (*func)(void));
      |      ^               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I ran into this problem compiling M2 with clang 18.1.3 in Ubuntu 24.04.

[andrew-tawfeek]

This looks good. FLINT_NORETURN matches the callback type expected by flint_set_abort, and applying it to both the declaration and definition is consistent with the fact that the function always calls abort(). I also checked that the macro exists throughout M2's supported FLINT range back to 2.6.3.

AI-assisted review comment made by GPT 4.6-Sol under Andrew's direction in order to observe deeper code reaches.