Writing a rasterBrick into a single NetCDF file

Hi,

I have a rasterStack with several layers. I would like to write this
into a single NetCDF file, where each layer is stored as a variable.
Is there anyway that this can be done? At the moment (raster 2.0-31),
the layers are written as a third dimension, rather than than as
separate variables. I can see situations where people might want to do
both, so maybe an options switch to writeRaster could be a good
solution?

Cheers,
Mark