This file is in a location generally used for detached debugging symbols, but it appears to contain a complete copy of the executable or library instead of only the debugging symbols. Files in subdirectories of /usr/lib/debug mirroring the main file system should contain only debugging information generated by objcopy --only-keep-debug. Binaries or shared objects built with extra debugging should be installed directly in /usr/lib/debug or in subdirectories corresponding to the package, not in the directories that mirror the main file system.
If you are using dh_strip with the --dbg-package flag, don't also install the library in /usr/lib/debug. dh_strip does all the work for you.