reproduce (this is a W=1 build):
        git remote add bcachefs https://evilpiepirate.org/git/bcachefs.git
        git fetch --no-tags bcachefs master
        git checkout d523781cfc5e70cdb73bdc883a3271ca65e7206e

        # install loongarch cross compiling tool for clang build
        # apt-get install binutils-loongarch-linux-gnu
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=loongarch olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=loongarch SHELL=/bin/bash fs/bcachefs/