Name LESS cache/css output files same as input file.

module/VuFindTheme/src/VuFindTheme/View/Helper/HeadLink.php

@@ -109,7 +109,8 @@ class HeadLink extends \Zend\View\Helper\HeadLink
                     'cache_dir' => $home . 'css/less/',
                     'cache_method' => false,
                     'compress' => true,
-                    'import_dirs' => $directories
+                    'import_dirs' => $directories,
+                    'output' => str_replace('.less', '.css', $file)
                 )
             );
             $this->prependStylesheet($cssDirectory . $css_file_name);