/usr/lib/haskell-packages/ghc/lib/filestore-0.4.0.4/extra-packages is in libghc-filestore-dev 0.4.0.4-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1
libghc-filestore-data (>= 0.4.0.4)