/usr/lib/gcc/x86_64-linux-gnu/7/32/libitm.so is in lib32gcc-7-dev 7.3.0-16ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc/x86_64-linux-gnu/7/32/../../../../../lib32/libitm.so.1
/usr/lib/gcc/x86_64-linux-gnu/7/32/../../../../../lib32/libitm.so.1