v15
tc-build两步标准化，lxc arm64 Ubuntu18.04上构建
源码https://github.com/tomxi1997/Toolchain-for-aarch64-hosts/releases/tag/v14 ,配合aosp.tar.xz来获取唯一源码，使用 tc-build.tar.xz编译
编译安卓内核还需要gcc 4.9
https://github.com/tomxi1997/Toolchain-for-aarch64-hosts/releases/tag/v6