Preserve the externally defined variables in the configure paths dialog

Previously the variables that were defined externally weren't being
readded to the variable map, so they would not appear in the dialog
the next time.

(Cherry-picked from fedc6519cd)

common/dialogs/dialog_configure_paths.cpp

@@ -221,14 +221,17 @@ bool DIALOG_CONFIGURE_PATHS::TransferDataFromWindow()
 
     for( int row = 0; row < m_EnvVars->GetNumberRows(); ++row )
     {
-        wxString name = m_EnvVars->GetCellValue( row, EV_NAME_COL );
-        wxString path = m_EnvVars->GetCellValue( row, EV_PATH_COL );
-        wxString external = m_EnvVars->GetCellValue( row, EV_FLAG_COL );
+        wxString     name = m_EnvVars->GetCellValue( row, EV_NAME_COL );
+        wxString     path = m_EnvVars->GetCellValue( row, EV_PATH_COL );
+        wxString     external = m_EnvVars->GetCellValue( row, EV_FLAG_COL );
+        ENV_VAR_ITEM var( path );
 
         if( external.Length() )
-            continue;
-
-        if( name.IsEmpty() )
+        {
+            // Don't check for consistency on external variables, just use them as-is
+            var.SetDefinedExternally( true );
+        }
+        else if( name.IsEmpty() )
         {
             m_errorGrid = m_EnvVars;
             m_errorRow = row;
@@ -245,7 +248,7 @@ bool DIALOG_CONFIGURE_PATHS::TransferDataFromWindow()
             return false;
         }
 
-        envVarMap[ name ] = ENV_VAR_ITEM( path );
+        envVarMap[ name ] = var;
     }
 
     Pgm().SetLocalEnvVariables( envVarMap );