Add flag to build with integer-simple

[michaelpj]

It would be nice to have a flag to enable building with integer-simple, even if it was slower.

Reason for asking: HLS builds some static binaries on an alpine distribution that forces integer-simple in GHC.

[Bodigrim]

I made a separate release without integer-gmp dependency, https://hackage.haskell.org/package/mod-0.0.0.0. Does it help?

Moving forward, I'll switch future versions of mod to ghc-bignum to let GHC to choose a numeric backend.

[michaelpj]

Thanks! Let me see if that makes a difference. Using ghc-bignum does seem like the way of the future indeed.

[Bodigrim]

Fixed in 86e1e35.