DirectMmap: Use off_t instead of off64_t for the offset parameter

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

absl/base/internal/direct_mmap.h

@@ -72,7 +72,7 @@ namespace base_internal {
 // Platform specific logic extracted from
 // https://chromium.googlesource.com/linux-syscall-support/+/master/linux_syscall_support.h
 inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
-                        off64_t offset) noexcept {
+                        off_t offset) noexcept {
 #if defined(__i386__) || defined(__ARM_ARCH_3__) || defined(__ARM_EABI__) || \
     defined(__m68k__) || defined(__sh__) ||                                  \
     (defined(__hppa__) && !defined(__LP64__)) ||                             \
@@ -102,7 +102,7 @@ inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
 #else
   return reinterpret_cast<void*>(
       syscall(SYS_mmap2, start, length, prot, flags, fd,
-              static_cast<off_t>(offset / pagesize)));
+              static_cast<unsigned long>(offset / pagesize)));  // NOLINT
 #endif
 #elif defined(__s390x__)
   // On s390x, mmap() arguments are passed in memory.