/usr/lib/x86_64-linux-gnu/libtcmalloc_debug.so is in libgoogle-perftools-dev 2.5-2.2ubuntu3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libtcmalloc_debug.so.4.3.0
/usr/lib/x86_64-linux-gnu/libtcmalloc_debug.so.4.3.0