Function build_walker_single_threaded 

pub fn build_walker_single_threaded(root: &Path) -> WalkBuilder

Build a WalkBuilder with the same defaults as build_default_walker plus threads(1).

threads(1) only constrains build_parallel(): the sequential build() never spawns the ignore thread pool (verified against the ignore 0.4.34 source, where only build_parallel reads the setting), so this helper is equivalent to build_default_walker for .build() callers. Prefer it only when the walker may go parallel.