/usr/arm-linux-gnueabihf/bin/ar is in binutils-arm-linux-gnueabihf 2.26.1-1ubuntu1~16.04.8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/arm-linux-gnueabihf/bin/../../bin/arm-linux-gnueabihf-ar