ROOT 6.10.06 build failure on macOS 10.13 Xcode 9

[ksmith]

@eguiraud

Another option is installing TBB yourself and ROOT should detect and use your system installation.

TBB is in many of the repos as well. This is what solved my issue when the TBB server was down:

Cannot build ROOT 6.10.04 (TBB-download fails)

The problem is not that the package does not exist, but that https://lcgpackages.web.cern.ch/lcgpackages/tarFiles/sources is currently down. Please use system TBB or try again later. The repository should be back up soon. Cheers,