Fix writing pad layer information to the board file

Pads should write that they exist on all layers using the wildcard and
then not also enumerate the copper layers (in this case, enumerating the
copper layers that were not enabled on the board).

pcbnew/pcb_io/kicad_sexpr/pcb_io_kicad_sexpr.cpp

@@ -1349,9 +1349,7 @@ void PCB_IO_KICAD_SEXPR::format( const FOOTPRINT* aFootprint ) const
 
 void PCB_IO_KICAD_SEXPR::formatLayers( LSET aLayerMask, bool aEnumerateLayers ) const
 {
-    static const LSET cu_all( LSET::AllCuMask( m_board
-                                                ? m_board->GetCopperLayerCount()
-                                                : MAX_CU_LAYERS ) );
+    static const LSET cu_all( LSET::AllCuMask() );
     static const LSET fr_bk(  { B_Cu, F_Cu } );
     static const LSET adhes(  { B_Adhes, F_Adhes } );
     static const LSET paste(  { B_Paste, F_Paste } );
@@ -1360,19 +1358,25 @@ void PCB_IO_KICAD_SEXPR::formatLayers( LSET aLayerMask, bool aEnumerateLayers )
     static const LSET crt_yd( { B_CrtYd, F_CrtYd } );
     static const LSET fab(    { B_Fab, F_Fab } );
 
-    LSET cu_mask = cu_all;
+    LSET cu_board_mask = LSET::AllCuMask( m_board
+                                           ? m_board->GetCopperLayerCount()
+                                           : MAX_CU_LAYERS );
 
     std::string output;
 
     if( !aEnumerateLayers )
     {
-        // output copper layers first, then non copper
-        if( ( aLayerMask & cu_mask ) == cu_mask )
+        // If all copper layers present on the board are enabled, then output the wildcard
+        if( ( aLayerMask & cu_board_mask ) == cu_board_mask )
         {
             output += ' ' + m_out->Quotew( "*.Cu" );
-            aLayerMask &= ~cu_all;          // clear bits, so they are not output again below
+
+            // Clear all copper bits because pads might have internal layers that aren't part of the
+            // board enabled, and we don't want to output those in the layers listing if we already
+            // output the wildcard.
+            aLayerMask &= ~cu_all;
         }
-        else if( ( aLayerMask & cu_mask ) == fr_bk )
+        else if( ( aLayerMask & cu_board_mask ) == fr_bk )
         {
             output += ' ' + m_out->Quotew( "F&B.Cu" );
             aLayerMask &= ~fr_bk;