correctly link EUTelescope/LCIO when building nreader library

- added ADDITIONAL_LIBRARIES CMake variable to keep e.g. EUTel libs reference (empty otherwise)
- link against ${ADDITIONAL_LIBRARIES} for all executables and the main library
- fixes linker problems when building the native reader libary *and* any other executables
- cherry-picked from @1e6b3333d675cab6a07a302bf329a5bf3b11195a

Conflicts:
	main/exe/CMakeLists.txt