make GPU flags local to libgpu

    file(GLOB_RECURSE GPU_NOT_LIB_CU ${LAMMPS_LIB_SOURCE_DIR}/gpu/lal_pppm.cu)

    list(REMOVE_ITEM GPU_LIB_CU ${GPU_NOT_LIB_CU})

    # still missing a way to limit defines to GPU build only

    # something like cuda_compile_definitions()

    # one way is this, the other adding it to OPTIONS

    add_definitions(-D_${GPU_PREC})

    add_definitions(-DNV_KERNEL -DUCL_CUDADR)

    cuda_include_directories(${LAMMPS_LIB_SOURCE_DIR}/gpu ${LAMMPS_LIB_BINARY_DIR}/gpu)

    if(CUDPP_OPT)

      file(GLOB GPU_LIB_CUDPP_CU ${LAMMPS_LIB_SOURCE_DIR}/gpu/cudpp_mini/*.cu)

    endif()

    cuda_compile(GPU_OBJS ${GPU_LIB_CU} ${GPU_LIB_CUDPP_CU} OPTIONS $<$<BOOL:${BUILD_SHARED_LIBS}>:-Xcompiler=-fPIC>)    

    cuda_compile(GPU_OBJS ${GPU_LIB_CU} ${GPU_LIB_CUDPP_CU} OPTIONS

                 $<$<BOOL:${BUILD_SHARED_LIBS}>:-Xcompiler=-fPIC>

                 -DNV_KERNEL -DUCL_CUDADR -D_${GPU_PREC})    

    file(MAKE_DIRECTORY ${LAMMPS_LIB_BINARY_DIR}/gpu)

    foreach(CU_OBJ ${GPU_OBJS})