Bootstrap doesn't clone llvm-project if profiling is enabled

[Noratrieb]

When using profiler = true in the cargo.toml to enable profiling, having a local copy of src/llvm-project is required. If no such copy is present, errors about missing libraries are emitted and the build fails.

Expected behavior:
Bootstrap initializes the src/llvm-project submodule when profiler is enabled.

[jyn514]

This should be pretty easy to fix - call builder.update_submodule("src/llvm-project") in impl Step for compile::Std if profiling is enabled.

[Noratrieb]

@rustbot claim