libff: shared build on darwin

pkgs/development/libraries/libff/default.nix

@@ -14,6 +14,12 @@ stdenv.mkDerivation rec {
 
   cmakeFlags = [ "-DWITH_PROCPS=Off" ];
 
+  # CMake is hardcoded to always build static library which causes linker
+  # failure for Haskell applications depending on haskellPackages.hevm on macOS.
+  postPatch = stdenv.lib.optionalString stdenv.isDarwin ''
+    substituteInPlace libff/CMakeLists.txt --replace "STATIC" "SHARED"
+  '';
+
   nativeBuildInputs = [ cmake pkg-config ];
   buildInputs = [ boost gmp openssl ];