D012 - The build directory is overridable and Linux-local

Status: decided Date: 2026-09-26

BUILD and CARGO_TARGET_DIR point at a Linux-local path ($HOME/...), never a Windows mount. Every host-run step changes into $(BUILD) first, so files a run writes land there too.

Why: a Windows mount carries no execute bit, so a binary built into the tree cannot run, and symbols.txt comes from running the host binary. Writing a report across the mount also costs most of a host run's time.

Rejected: building in the repository tree - unrunnable output and slow writes.