add queue mechanism for builds and only allow one package built at a time for now.

frontend/lib/screens/build_screen.dart

@@ -24,7 +24,7 @@ class _BuildScreenState extends State<BuildScreen> {
       body: APIBuilder<BuildProvider, Build, BuildDTO>(
           dto: BuildDTO(buildID: widget.buildID),
           interval: const Duration(seconds: 10),
-          onLoad: () => const Text("no data"),
+          onLoad: () => const Text("loading"),
           onData: (buildData) {
             final start_time = DateTime.fromMillisecondsSinceEpoch(
                 (buildData.start_time ?? 0) * 1000);
@@ -64,11 +64,23 @@ class _BuildScreenState extends State<BuildScreen> {
                 const SizedBox(
                   height: 15,
                 ),
-                BuildOutput(build: buildData)
+                _buildPage(buildData)
               ],
             );
           }),
       appBar: AppBar(),
     );
   }
+
+  Widget _buildPage(Build build) {
+    switch (build.status) {
+      case 3:
+        return const Text("in Queue");
+      case 0:
+      case 1:
+      case 2:
+      default:
+        return BuildOutput(build: build);
+    }
+  }
 }

frontend/lib/screens/package_screen.dart

@@ -1,6 +1,3 @@
-import 'dart:async';
-
-import 'package:aurcache/api/builds.dart';
 import 'package:aurcache/api/packages.dart';
 import 'package:aurcache/components/api/APIBuilder.dart';
 import 'package:aurcache/providers/builds_provider.dart';