[181x](haasui): add haasui v1.5(musl) Change-Id: I473ef3a00863533b1b13230c4ce9eff0997c08c4
we have these folders in this repo: prebuild: to store header files and libraries for cross compling. target: file to build up a root filesystem. there are two subfolders: 1. common: for platform independent files 2. overlay: for platform dependent files when building rootfs, files in overlay folder will be merged into common folder. tools: bin and scritps for generating rootfs configs: we have two types of configuration file: 1. txt: for file list in ramdisk 2. its: for generating itb file