fstatat yields wrong results on macOS/x86_64

[s-ludwig]

The fstatat declaration introduced by DMD 2.112.0 uses the wrong mangling on x86_64, leading to the fields of the stat_t result being mixed up.

[ibuclaw]

@s-ludwig is that

pragma(mangle, "fstatat$INODE64")

?

[s-ludwig]

@ibuclaw, has already been fixed by #22689 - I thought mentioning the issue in the title would work, but it didn't.