home: xdg: move 'less' variables to their module

It's been abandoned, `nil` is a better language server nowadays.

modules/home/gdb/default.nix

@@ -26,14 +26,7 @@ in
         gdb
       ];
 
-      xdg = {
-        configFile."gdb/gdbinit".source = ./gdbinit;
-        dataFile. "gdb/.keep".text = "";
-      };
-
-      home.sessionVariables = {
-        GDBHISTFILE = "${config.xdg.dataHome}/gdb/gdb_history";
-      };
+      xdg.configFile."gdb/gdbinit".source = ./gdbinit;
     }
 
     (lib.mkIf cfg.rr.enable {

modules/home/vim/plugin/settings/null-ls.lua

@@ -31,9 +31,11 @@ null_ls.register({
 -- Nix
 null_ls.register({
     null_ls.builtins.formatting.nixpkgs_fmt.with({
-        -- Only used if available, but prefer LSP if available
+        -- Only used if available, but prefer rnix if available
         condition = function()
-            return utils.is_executable("nixpkgs-fmt") and not utils.is_executable("nil")
+            return utils.is_executable("nixpkgs-fmt")
+                and not utils.is_executable("rnix-lsp")
+                and not utils.is_executable("nil")
         end,
     }),
 })

modules/home/xdg/default.nix

@@ -42,6 +42,7 @@ in
     ANDROID_USER_HOME = "${configHome}/android";
     CARGO_HOME = "${dataHome}/cargo";
     DOCKER_CONFIG = "${configHome}/docker";
+    GDBHISTFILE = "${dataHome}/gdb/gdb_history";
     GRADLE_USER_HOME = "${dataHome}/gradle";
     HISTFILE = "${dataHome}/bash/history";
     INPUTRC = "${configHome}/readline/inputrc";