Update lib-nccl to master

[psyhtest]

After a recent update of NCCL to 2.3.5-5 (25 September 2018), make install no longer works (the install target has been deprecated?).

For now, I've fixed the Git commit to the one just before this update (29 November 2017) in the meta of package:lib-nccl, but we should eventually update the installation script.

/cc @fvella @gfursin