Set up nix tooling

nix/shell.nix

@@ -0,0 +1,51 @@
+{ pkgs, lib }:
+pkgs.mkShell {
+  nativeBuildInputs = with pkgs; [
+    autoconf
+    automake
+    autogen
+    autoreconfHook
+
+    pkg-config
+    python3
+    perl
+    bison
+    flex
+    perlPackages.JSON
+    texinfo
+
+    # check inputs
+    curl
+    jdk_headless
+    unzip
+    which
+  ];
+
+  buildInputs = with pkgs; [
+    db
+    libedit
+    pam
+    cjson
+    libcap_ng
+    libmicrohttpd
+    openldap
+    openssl
+    sqlite
+  ];
+
+  env = {
+    CFLAGS = lib.concatStringsSep " " [
+      # From github workflows
+      "-Wno-error=shadow"
+      "-Wno-error=bad-function-cast"
+      "-Wno-error=unused-function"
+      "-Wno-error=unused-result"
+      "-Wno-error=deprecated-declarations"
+
+      # idk, but it complained about these during compilation.
+      # maybe they come from the nix environment, or too new compiler?
+      "-Wno-error=maybe-uninitialized"
+      "-Wno-error=format-overflow"
+    ];
+  };
+}