Try adding initial /build-tmpfs then copying or mounting /lib{n} ... then making new /specific-build-tmps with subdirectories or readonly for mounts /lib{n}. Th

Try adding initial /build-tmpfs then copying or mounting /lib{n} ... then making new /specific-build-tmps with subdirectories or readonly for mounts /lib{n}. This way writes are discarded after a build (you destroy /specific-build on completion). If you can't easily split files between disparate sources, use a COW filesystem only for /specific/build/tmpfs. Likely to exhibit substantially different performance characteristics, with easily limited memory requirements. Did a lot of this with ZFS in the past, worked very well.