Kicad PROJECT_ARCHIVER: better fix than commit 734e0ca0:

Do not store twice files with extension .gm?? in zip files
Previous commit did not store files like *.gm12, that can be existing when
Gerber files come from another ECAD tool, and allowed duplicate files like *.g1

common/project/project_archiver.cpp

@@ -137,8 +137,10 @@ bool PROJECT_ARCHIVER::Archive( const wxString& aSrcDir, const wxString& aDestFi
             wxT( "*.stp" ), wxT( "*.step" ),        // 3d files
             wxT( "*.wrl" ),
             wxT( "*.g?" ), wxT( "*.g??" ),          // Gerber files
+            wxT( "*.gm??"),                         // Some gerbers like .gm12 (from protel export)
             wxT( "*.gbrjob" ),                      // Gerber job files
-            wxT( "*.pos" ), wxT( "*.drl" ), wxT( "*.nc" ), wxT( "*.xnc" ),  // Fab files
+            wxT( "*.pos" ),                         // our position files
+            wxT( "*.drl" ), wxT( "*.nc" ), wxT( "*.xnc" ),  // Fab drill files
             wxT( "*.d356" ),
             wxT( "*.rpt" ),
             wxT( "*.net" ),
@@ -197,8 +199,18 @@ bool PROJECT_ARCHIVER::Archive( const wxString& aSrcDir, const wxString& aDestFi
 
     unsigned long uncompressedBytes = 0;
 
+    // Our filename collector can store duplicate filenames. for instance *.gm2
+    // matches both *.g?? and *.gm??.
+    // So skip duplicate filenames (they are sorted, so it is easy.
+    wxString lastStoredFile;
+
     for( unsigned ii = 0; ii < files.GetCount(); ii++ )
     {
+        if( lastStoredFile == files[ii] )   // duplicate name: already stored
+            continue;
+
+        lastStoredFile = files[ii];
+
         wxFileSystem fsfile;
 
         wxFileName curr_fn( files[ii] );