Created attachment 198785 [details]
GCC architectures require linking with libosgDB.
While here, remove support for Clang < 4.0 (only in 10.3, goes EOL tomorrow) and GCC < 6 (we use GCC7 on GCC architectures anyway).
Tested on powerpc64 and amd64.
A commit references this bug:
Date: Thu Nov 8 19:29:15 UTC 2018
New revision: 484471
devel/simgear: GCC architectures require linking with libosgDB 
Also, remove support for Clang < 4.0 and GCC < 6 for devel/simgear  and
PR: 232832 
Submitted by: Piotr Kubaj <email@example.com>