reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/staging.git/commit/?id=ea370e1e782a07c1c22bce146c82765451fdcb11
        git remote add bigeasy-staging https://git.kernel.org/pub/scm/linux/kernel/git/bigeasy/staging.git
        git fetch --no-tags bigeasy-staging arm_warning
        git checkout ea370e1e782a07c1c22bce146c82765451fdcb11

        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse: v0.6.5-rc1

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=arm SHELL=/bin/bash