off_t is best for portability. Its size varies with the platform.
off64_t is non-standard, but is present in glibc and some BSDs.
It also matches the signature specified in the manual.
https://man7.org/linux/man-pages/man2/mmap.2.html

This is a re-spin of #1349, but correctly casts the type to the type
expected by the kernel for mmap2.
https://man7.org/linux/man-pages/man2/mmap2.2.html

Fixes #1473

PiperOrigin-RevId: 539656313
Change-Id: I7a30dd9d3eb6af03a99da0d93d721a86f6521b25