/usr/lib/gcc/x86_64-w64-mingw32/4.9-posix/liblto_plugin.so is in gcc-mingw-w64-x86-64 4.9.1-19+14.3.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/gcc/x86_64-w64-mingw32/4.9-posix/liblto_plugin.so.0.0.0