/usr/lib/gcc/x86_64-linux-gnu/ is in fixincludes 1:4.8.2-19ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/gcc/x86_64-linux-gnu/4.8/
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/fixinc.sh
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/fixinc_list
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/fixincl
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/gsyslimits.h
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/include/
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/include/README
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/include/limits.h
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/macro_list
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/mkheaders
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/mkheaders.conf
/usr/lib/gcc/x86_64-linux-gnu/4.8/install-tools/mkinstalldirs