reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install mips cross compiling tool for clang build
        # apt-get install binutils-mipsel-linux-gnu
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git/commit/?id=fae7938dfe0ba5302ee34640a53a85c6305ad99c
        git remote add brauner-vfs https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
        git fetch --no-tags brauner-vfs work.coredump.socket
        git checkout fae7938dfe0ba5302ee34640a53a85c6305ad99c
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=mips olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=mips SHELL=/bin/bash net/