internal/syscall/unix: fix PosixFallocate on 32-bit freebsd
Follow-up for CL 478035 which broke the freebsd/396 builders:
https://build.golang.org/log/
e6e442cd353024c4fdb64111ad0bcbf5b25b8ecd
64-bit syscall arguments need to be passed as two 32-bit arguments on
32-bit freebsd.
Change-Id: Idf4fdf4ab7d112bc2cf95b075a5a29f221bffcb6
Reviewed-on: https://go-review.googlesource.com/c/go/+/479715
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>