Try to do the right thing for linking netCDF::netcdf

[dschwoerer]

This will certainly fail in some cases, but I think there is in general no easy way to get the needed flags for linking. If anybody has better ideas: great :-)

[ZedThree]

Seems like a reasonable attempt!

That whole bit is getting quite long now, but be nice to pull it out into a configure_bout_config_script function somewhere else to keep the main CMakeFiles.txt a bit tidier