reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git/commit/?id=cc9194fde2133f928cc0bdf25bb2929948f9da89
        git remote add mhiramat https://git.kernel.org/pub/scm/linux/kernel/git/mhiramat/linux.git
        git fetch --no-tags mhiramat topic/fprobe-on-fgraph
        git checkout cc9194fde2133f928cc0bdf25bb2929948f9da89
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/trace/