Use musl on Linux

flake.nix

@@ -15,7 +15,10 @@
   outputs = { self, nixpkgs, flake-utils, nix-bundle-exe, ... }:
     flake-utils.lib.eachDefaultSystem (system:
       let
-        pkgs = nixpkgs.legacyPackages.${system};
+        systemPkgs = nixpkgs.legacyPackages.${system};
+        # prefer musl on Linux, static glibc + threading does not work properly
+        # TODO: maybe only override it for echidna-redistributable?
+        pkgs = if systemPkgs.stdenv.hostPlatform.isLinux then systemPkgs.pkgsMusl else systemPkgs;
         # this is not perfect for development as it hardcodes solc to 0.5.7, test suite runs fine though
         # would be great to integrate solc-select to be more flexible, improve this in future
         solc = pkgs.stdenv.mkDerivation {