BuildTools: Dont print duplicate ComBases

This can happen when something has 2 ComBases that were typemapped to
IUnknown

Author: Beyley

src/Core/Silk.NET.BuildTools/Bind/StructWriter.cs

@@ -194,7 +194,7 @@ public static void WriteStruct
                 sw.WriteLine();
             }
 
-            foreach (var comBase in @struct.ComBases)
+            foreach (var comBase in @struct.ComBases.RemoveDuplicates())
             {
                 var asSuffix = comBase.Split('.').Last();
                 asSuffix = asSuffix.StartsWith('I') ? asSuffix.Substring(1) : comBase;