Benchmarking no longer works after rust-lang/rust#68708

[ssomers]

#68708 suspended the ability to benchmark liballoc (and probably others, but not everything). x.py bench (with or without --stage 0) now lists oodles of errors starting with:

Compiling getrandom v0.1.14
error: duplicate lang item in crate `core` (which `rustc_std_workspace_core` depends on): `bool`.
  |
  = note: first defined in crate `core` (which `getrandom` depends on)

It's still possible though to build and test benchmarks with say x.py test --stage 0 --no-doc.

[Mark-Simulacrum]

Hm, it could be that some of those Lang items need to be cfg(not(test)) or so.

[ssomers]

Issue appears resolved by #71439