dpkg: sync_file_range

No crash. Workflow to produce BSC is as follows: run Ubuntu-in-ish within chroot.
Copied from the console This is not issue #825, which was an ‘illegal instruction’.
```
root@iPhone:/# cd root
root@iPhone:~# dpkg -i gcc-8-base_8.4.0-1ubuntu1~18.04_i386.deb
Selecting previously unselected package gcc-8-base:i386.
(Reading database ... 4093 files and directories currently installed.)
Preparing to unpack gcc-8-base_8.4.0-1ubuntu1~18.04_i386.deb ...
Unpacking gcc-8-base:i386 (8.4.0-1ubuntu1~18.04) ...
Bad system call
root@iPhone:~# dmesg
[ 0.000000] 835 missing syscall 314
```

No source file or test is named. Reproduce the Ubuntu-in-ish chroot workflow, then inspect handling of missing syscall 314, `sync_file_range`, using the `dmesg` output as the baseline; done means the dpkg installation no longer stops with `Bad system call`.

Written by the indexing model from the issue text.