reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace.git/commit/?id=ca9f90f1a871d6778fad8958e2e2bda27c3b29d5
        git remote add trace https://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace
        git fetch --no-tags trace unwind/sframe
        git checkout ca9f90f1a871d6778fad8958e2e2bda27c3b29d5
        # 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