reproduce (this is a W=1 build):
        # https://github.com/avpatel/linux/commit/07c38c2b100fdff5878133f41eb7875af40ab366
        git remote add avpatel https://github.com/avpatel/linux.git
        git fetch --no-tags avpatel riscv_trace_acpi_support_v1
        git checkout 07c38c2b100fdff5878133f41eb7875af40ab366
        # apt-get install llvm-dev

        # save the config file
        make W=1 ARCH=i386 olddefconfig
        make W=1 ARCH=i386 
        make W=1 headers_install
        make W=1 -C tools/testing/selftests