gnustep-gui-runtime: Multiple libobjc.so version linked due to mix of dependencies

[Joost Yervante Damad <joost@damad.be>]

Hello,

I've been looking into issue 672986 and it seems all that is needed is a 
rebuild of gnustep-gui-0.20.0 and after that a rebuild of it's reverse 
dependencies to get rid of the double libobjc.so linkage.

I've tested this locally by rebuilding gnustep-gui-0.20.0 and 
terminal.app-0.9.8 on wheezy AMD64.

Greetings, Joost Damad