Fix girder not having correct physics layers, add TileNotBlocked construction condition

Content.Shared/Construction/ConstructionConditions/TileNotBlocked.cs

@@ -0,0 +1,32 @@
+using Content.Shared.Maps;
+using JetBrains.Annotations;
+using Robust.Shared.Interfaces.GameObjects;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.Construction.ConstructionConditions
+{
+    [UsedImplicitly]
+    public class TileNotBlocked : IConstructionCondition
+    {
+        private bool _filterMobs = false;
+        private bool _failIfSpace = true;
+
+        public void ExposeData(ObjectSerializer serializer)
+        {
+            serializer.DataField(ref _filterMobs, "filterMobs", false);
+            serializer.DataField(ref _failIfSpace, "failIfSpace", true);
+        }
+
+        public bool Condition(IEntity user, EntityCoordinates location, Direction direction)
+        {
+            var tileRef = location.GetTileRef();
+
+            if (tileRef == null || tileRef.Value.IsSpace())
+                return !_failIfSpace;
+
+            return !tileRef.Value.IsBlockedTurf(_filterMobs);
+        }
+    }
+}

Content.Shared/Construction/ConstructionPrototype.cs

@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Serialization;
 using Robust.Shared.Utility;