shell.nix: add binutils and gcc

Fixes b.hswaw.net/33

Change-Id: Iadeb4157f4271ad684b6c2603d734cb0c098238d
diff --git a/shell.nix b/shell.nix
index cb39fe4..3e0bdc4 100644
--- a/shell.nix
+++ b/shell.nix
@@ -24,6 +24,7 @@
     openjdk11
     openldap.dev cyrus_sasl.dev # for python-ldap
     wkhtmltopdf
+    gcc binutils
   ];
   multiPkgs = pkgs: [
     (pkgs.runCommand "protocols" {}