mbx-v0.1.0

Added

• (release) publish prebuilt binaries on a tag (#14)
• (session) log why each compilation was not cached (#11)
• (session) count compilations the cache declined (#10)
• (cli) add build, gc, and cache commands (#7)
• (session) add the cache session and rustc shim (#6)

Other

• (cli) stop the target-dir probe test reading the ambient environment (#15)
• qualify cross-checkout sharing, and test the boundary (#12)
• (session) stop fsyncing restored outputs (#9)
• add workspace scaffolding and CI (#2)