Don't test on MacOS

See tweag#256,
there are precision issues on macs.

flake.nix

@@ -76,6 +76,9 @@
             name = "monad-bayes";
             root = src;
             cabal2nixOptions = "--benchmark -fdev";
+
+            # https://github.com/tweag/monad-bayes/pull/256: Don't run tests on Mac because of machine precision issues
+            modifier = drv: if system == "x86_64-linux" then drv else pkgs.haskell.lib.dontCheck drv;
           };
           ghcs = [ # Always keep this up to date with the tested-with section in monad-bayes.cabal!
             "ghc902"
@@ -85,6 +88,7 @@
           in lib.attrsets.genAttrs ghcs buildForVersion;
 
         monad-bayes = monad-bayes-per-ghc.ghc902;
+
         monad-bayes-all-ghcs = pkgs.linkFarm "monad-bayes-all-ghcs" monad-bayes-per-ghc;
 
         jupyterEnvironment = mkJupyterlabFromPath ./kernels {inherit pkgs monad-bayes;};