lang/vim crashes when build on ubuntu

[Aleksej Lebedev <root%zta.lk@localhost>]

Hi, everyone!

For quite some time ubuntu is shipping gcc with _FORTIFY_SOURCE=2 
defined by default.
This makes vim crash.

Here is the discussion: 
https://groups.google.com/forum/#!msg/vim_dev/HU5aZfCv4iM/aHZlX67jcsEJ

I encountered it first time in ubuntu-18.04, but root cause is known for 
quite a while.

I am not quite sure what would be the best way to pass _FORTIFY_SOURCE=1 
from pkgsrc.
So I am not providing the patch yet. But maybe it's immediately clear 
for morr%NetBSD.org@localhost ;-).

--
Aleksej Lebedev