reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git/commit/?id=ed21c8550606f50c81489835db05770cc199bf16
        git remote add ast-bpf https://git.kernel.org/pub/scm/linux/kernel/git/ast/bpf.git
        git fetch --no-tags ast-bpf uptr_v3
        git checkout ed21c8550606f50c81489835db05770cc199bf16
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash kernel/bpf/