feat: oci packer can now use mksquashfs if available (#70)

* feat: oci packer can now use mksquashfs if available

* fix: use nproc in kernel build script for default jobs, and fix DEV.md guide

* feat: working erofs backend

Cargo.toml

@@ -42,6 +42,7 @@ fancy-duration = "0.9.2"
 flate2 = "1.0"
 futures = "0.3.30"
 human_bytes = "0.4"
+indexmap = "2.2.6"
 indicatif = "0.17.8"
 ipnetwork = "0.20.0"
 libc = "0.2"