Cannot build without libgmp

[LegNeato]

Using the following in Cargo.toml:

openlimits = { version = "0.3", default-features = false, features = ["num_bigint"]}

Fails:

rust-bigint-1.2.0/src/lib.rs:36:1
   |
24 | pub type BigInt = gmp::mpz::Mpz;
   | -------------------------------- previous definition of the type `BigInt` here
...
36 | pub type BigInt = num_bigint::BigInt;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `BigInt` redefined here
   |
   = note: `BigInt` must be defined only once in the type namespace of this module