plugins: try harder to compile alarm_speech on linux

Using GNUStep. Modified from a debian patch of Janos Guljas.
uwsgiconfig: force no-format-security too

It may happen that a plugin is using -Wformat -Wformat-security so need to remove
both otherwise as seen in emperor_pg plugin:

 cc1: error: -Wformat-security ignored without -Wformat [-Werror=format-security]

Based on a debian patch of Janos Guljas.
Merge pull request #336 from xrmx/debian-fixes

A couple of patches from debian packaging