Function with_lock 

pub fn with_lock<F: FnOnce() -> R, R>(lock_path: &Path) -> impl FnOnce(F) -> R

Run f while holding an exclusive cross-process lock on lock_path.

A build script may be invoked concurrently for multiple compile units of the same crate (e.g. the host-profile build-dep unit and the target-profile unit of a links crate). This serializes a download/extract block via an atomic-create lock file so concurrent invocations don’t race on shared writes; the second waiter typically observes a fresh marker and skips its own work. A lock held longer than 120 s (e.g. a crashed previous holder) is treated as stale, removed, and the wait continues.