uboot: (firmwareOdroidC2/C4) don't invoke patch tool, use patches = [] instead

https://github.com/NixOS/nixpkgs/blob/master/pkgs/stdenv/generic/setup.sh#L948
this can do it nicely.

Signed-off-by: Anton Arapov <anton@deadbeef.mx>

nixos/modules/config/system-environment.nix

@@ -0,0 +1,104 @@
+# This module defines a system-wide environment that will be
+# initialised by pam_env (that is, not only in shells).
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+
+  cfg = config.environment;
+
+in
+
+{
+
+  options = {
+
+    environment.sessionVariables = mkOption {
+      default = {};
+      description = ''
+        A set of environment variables used in the global environment.
+        These variables will be set by PAM early in the login process.
+
+        The value of each session variable can be either a string or a
+        list of strings. The latter is concatenated, interspersed with
+        colon characters.
+
+        Note, due to limitations in the PAM format values may not
+        contain the <literal>"</literal> character.
+
+        Also, these variables are merged into
+        <xref linkend="opt-environment.variables"/> and it is
+        therefore not possible to use PAM style variables such as
+        <code>@{HOME}</code>.
+      '';
+      type = with types; attrsOf (either str (listOf str));
+      apply = mapAttrs (n: v: if isList v then concatStringsSep ":" v else v);
+    };
+
+    environment.profileRelativeSessionVariables = mkOption {
+      type = types.attrsOf (types.listOf types.str);
+      example = { PATH = [ "/bin" ]; MANPATH = [ "/man" "/share/man" ]; };
+      description = ''
+        Attribute set of environment variable used in the global
+        environment. These variables will be set by PAM early in the
+        login process.
+
+        Variable substitution is available as described in
+        <citerefentry>
+          <refentrytitle>pam_env.conf</refentrytitle>
+          <manvolnum>5</manvolnum>
+        </citerefentry>.
+
+        Each attribute maps to a list of relative paths. Each relative
+        path is appended to the each profile of
+        <option>environment.profiles</option> to form the content of
+        the corresponding environment variable.
+
+        Also, these variables are merged into
+        <xref linkend="opt-environment.profileRelativeEnvVars"/> and it is
+        therefore not possible to use PAM style variables such as
+        <code>@{HOME}</code>.
+      '';
+    };
+
+  };
+
+  config = {
+    environment.etc."pam/environment".text = let
+      suffixedVariables =
+        flip mapAttrs cfg.profileRelativeSessionVariables (envVar: suffixes:
+          flip concatMap cfg.profiles (profile:
+            map (suffix: "${profile}${suffix}") suffixes
+          )
+        );
+
+      # We're trying to use the same syntax for PAM variables and env variables.
+      # That means we need to map the env variables that people might use to their
+      # equivalent PAM variable.
+      replaceEnvVars = replaceStrings ["$HOME" "$USER"] ["@{HOME}" "@{PAM_USER}"];
+
+      pamVariable = n: v:
+        ''${n}   DEFAULT="${concatStringsSep ":" (map replaceEnvVars (toList v))}"'';
+
+      pamVariables =
+        concatStringsSep "\n"
+        (mapAttrsToList pamVariable
+        (zipAttrsWith (n: concatLists)
+          [
+            # Make sure security wrappers are prioritized without polluting
+            # shell environments with an extra entry. Sessions which depend on
+            # pam for its environment will otherwise have eg. broken sudo. In
+            # particular Gnome Shell sometimes fails to source a proper
+            # environment from a shell.
+            { PATH = [ config.security.wrapperDir ]; }
+
+            (mapAttrs (n: toList) cfg.sessionVariables)
+            suffixedVariables
+          ]));
+    in ''
+      ${pamVariables}
+    '';
+  };
+
+}