eternal-terminal: fix build w/glibc-2.34

Failing Hydra build: https://hydra.nixos.org/build/154077447

pkgs/tools/networking/eternal-terminal/default.nix

···
 , openssl
 , protobuf
 , zlib
+, catch2
 }:
 
 stdenv.mkDerivation rec {
···
     rev = "et-v${version}";
     hash = "sha256-cCZbG0CD5V/FTj1BuVr083EJ+BCgIcKHomNtpJb3lOo=";
   };
+
+  preBuild = ''
+    cp ${catch2}/include/catch2/catch.hpp ../external_imported/Catch2/single_include/catch2/catch.hpp
+  '';
 
   nativeBuildInputs = [
     cmake
···
   CXXFLAGS = lib.optional stdenv.cc.isClang [
     "-std=c++17"
   ];
+
+  doCheck = true;
 
   meta = with lib; {
     description = "Remote shell that automatically reconnects without interrupting the session";