reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git/commit/?id=435f15904e62d96d0c9029e147fb9c8dfbdc11a3
        git remote add jpoimboe https://git.kernel.org/pub/scm/linux/kernel/git/jpoimboe/linux.git
        git fetch --no-tags jpoimboe objtool/core
        git checkout 435f15904e62d96d0c9029e147fb9c8dfbdc11a3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash