Call for Testing: Build Dir Layout v2

The blog post is a call for testing the new build directory layout in Cargo, inviting developers to report issues with the nightly-only flag -Zbuild-dir-new-layout. It outlines how to perform tests with the new layout, potential failure modes, and the planned changes to improve build performance and organization of build artifacts in Rust projects. The proposed changes aim to facilitate cross-workspace caching, automatic cleanup of stale build units, and better management of intermediate artifacts.