Bug#886515: update symbols file for arm64 and mark tests failing on launchpad

[Matthias Klose]

Package: src:ruby2.5
Version: 2.5.0-4
Tags: patch

- update symbols file for arm64
- mark tests failing on launchpad (as done for 2.3)

patch at
https://patches.ubuntu.com/r/ruby2.5/ruby2.5_2.5.0-4ubuntu1.patch