We don't use any GNU-specific printf args, but this prevents warnings about
%z, observed on MinGW even though every libc anyone is likely to use there
supports %z perfectly well, and we're not stopping using it just because
MinGW complains. Doing this means we stand more chance of seeing *actual*
problems on such platforms without them being drowned in noise.
We turn this off on clang, which doesn't support __gnu_printf__.
Suggested by Eli Zaretskii.
libctf/
PR libctf/31863
* ctf-impl.h (_libctf_printflike_): Use __gnu_printf__.
f86f9fd859