CMake FindOmniORB silently fail to find libraries

This results in a lot of undefined reference to OmniORB symbols.

I noticed this issue when creating a new Conda environment.

• something has changed with the Conda packaging of OmniORB
• the FindOmniORB.cmake is seriously old school and buggy (imported from another random project)

• Rewrite a clean FindOmniORB.cmake