journalbeat7: fix binary by setting RPATH to systemd using patchelf

(cherry picked from commit 42c9c6df73)

pkgs/misc/logging/beats/7.x.nix

@@ -45,5 +45,8 @@ in {
       journal entries from Linuxes with systemd.
     '';
     buildInputs = [ systemd.dev ];
+    postFixup = let libPath = stdenv.lib.makeLibraryPath [ systemd.lib ]; in ''
+      patchelf --set-rpath ${libPath} "$bin/bin/journalbeat"
+    '';
   };
 }