Downstream RPATH overwritten

Created by: ax3l

I am using the ADIOS2Config.cmake module for v2.5.0 downstream in openPMD-api.

Somehow, the ADIOS2 CMakeLists.txt lines overwrite my downstream -DCMAKE_INSTALL_RPATH=$ORIGIN setting to read $ORIGIN/.libsopenpmd_api instead of $ORIGIN.

https://github.com/ornladios/ADIOS2/blob/v2.5.0/CMakeLists.txt#L156-L179

As soon as I am not linking to ADIOS2 anymore, the problem is gone.

Probably we should only set the rpath as CMake property on targets or append to already set, user-provided CMAKE_INSTALL_RPATH locations?