Fails on Manjaro 17 (Arch) due to plugins.cfg path differences

[RMKD]

Loading library /usr/lib/x86_64-linux-gnu/OGRE-1.9.0/RenderSystem_GL
An exception has occured: OGRE EXCEPTION(7:InternalErrorException): Could not load dynamic library /usr/lib/x86_64-linux-gnu/OGRE-1.9.0/RenderSystem_GL.  System Error: /usr/lib/x86_64-linux-gnu/OGRE-1.9.0/RenderSystem_GL.so.1.9.0: cannot open shared object file: No such file or directory in DynLib::load at /build/ogre/src/ogre/OgreMain/src/OgreDynLib.cpp (line 109)
*** Error in `./OpenHMDDemo': free(): invalid pointer: 0x00007ffe934ac4e0 ***

quick fix: in plugins.cfg, change PluginsFolder value from /usr/lib/x86_64-linux-gnu/OGRE-1.9.0/ to /usr/lib64/OGRE/ (or wherever your installer put OGRE)

long-term fix: autodetect the location in the cmake process?