Ensure archives without ext are given .zip

Fixes https://gitlab.com/kicad/code/kicad/-/issues/21423

common/jobs/jobs_output_archive.cpp

@@ -24,6 +24,7 @@
 #include <wx/zipstrm.h>
 #include <gestfich.h>
 #include <common.h>
+#include <wildcards_and_files_ext.h>
 
 JOBS_OUTPUT_ARCHIVE::JOBS_OUTPUT_ARCHIVE() :
     JOBS_OUTPUT_HANDLER(),
@@ -52,6 +53,8 @@ bool JOBS_OUTPUT_ARCHIVE::HandleOutputs( const wxString& baseTempPath, PROJECT*
     if( outputPath.StartsWith( "~" ) )
         outputPath.Replace( "~", wxGetHomeDir(), false );
 
+    outputPath = EnsureFileExtension( outputPath, FILEEXT::ArchiveFileExtension );
+
     wxFFileOutputStream ostream( outputPath );
 
     if( !ostream.IsOk() ) // issue to create the file. Perhaps not writable dir

kicad/dialogs/dialog_destination.cpp

@@ -104,7 +104,19 @@ void DIALOG_DESTINATION::onOutputPathBrowseClicked(wxCommandEvent& event)
         if( dlg.ShowModal() != wxID_OK )
             return;
 
-        m_textCtrlOutputPath->SetValue( dlg.GetPath() );
+        wxString path = dlg.GetPath();
+
+        if( m_destination->m_type == JOBSET_DESTINATION_T::ARCHIVE )
+        {
+            wxFileName fn( path );
+
+            if( fn.GetExt().IsEmpty() )
+                fn.SetExt( FILEEXT::ArchiveFileExtension );
+
+            path = fn.GetFullPath();
+        }
+
+        m_textCtrlOutputPath->SetValue( path );
     }
 
 }