Alternative to LGPL-dependency integer-gmp

When I try to compile linear with a ghc-Version without "integer-gmp" (used "integer-simple" instead), there is the error that the library "integer-gmp" can't be found. Also the flags "+integer-simple" and "-integer-gmp" set in the file cabal.project don't seem to work.
The request is to provide an alternative integer library, that the user can choose with a flag. I don't know where the dependency of libgmp lies and if it's an easy task to remove it, since linear depends on lots of packages.
This feature would be useful to use linear in a closed-source setting on windows.