build-catalogue doesn't build GPU mechanisms

[noraabiakar]

The build-catalogue script generates the GPU mechanisms but does not build them.

Part of the issue is the missing -B gpu flag in the call to generate_catalogue (the ARB_WITH_GPU cmake flag isn't set in the arbor-config file). But fixing that will only enable the compilation of the .cpp files of the GPU mechanisms, not the .cu files, which may need to be compiled by a different compiler.

[llandsmeer]

+1 I just finished the jupyter notebook that runs my model on arbor master. Works great on the CPU at 30s/10ms, but on the GPU it fails with RuntimeError: missing implementation for mechanism ca_conc in catalogue

[llandsmeer]

Even a --gpu flag to only build the GPU mechanisms but not the CPU ones would be perfect already - the network does not run on the CPU anyway