CMake in turbulence library mode #20

Building only the turbulence library using cmake with -DGOTM_BUILD_LIBRARIES_ONLY=true fails in the v6.0.0 release (and the master branch as well) due to a missing dependency on input when building airsea. I don't think airsea is needed in the turbulence library, right? So moving the following line after the check on GOTM_BUILD_LIBRARIES_ONLY seems to fix this. I didn't check if this change breaks the building with FABM etc though... @bolding @jornbr