MDL-31685 new setting for prevention of file based locking

Please note that this setting can not be stored in database because some scripts use ABORT_AFTER_CONFIG.

config-dist.php

@@ -353,6 +353,10 @@ $CFG->admin = 'admin';
 //     $CFG->tempdir = '/var/www/moodle/temp';
 //     $CFG->cachedir = '/var/www/moodle/cache';
 //
+// Some filesystems such as NFS may not support file locking operations.
+// Locking resolves race conditions and is strongly recommended for production servers.
+//     $CFG->preventfilelocking = false;
+//
 // If $CFG->langstringcache is enabled (which should always be in production
 // environment), Moodle keeps aggregated strings in its own internal format
 // optimised for performance. By default, this on-disk cache is created in

lib/minify/config.php

@@ -17,7 +17,7 @@ $min_errorLogger = false;
 $min_allowDebugFlag = debugging('', DEBUG_DEVELOPER);
 $min_cachePath = $CFG->tempdir;
 $min_documentRoot = $CFG->dirroot.'/lib/minify';
-$min_cacheFileLocking = true;
+$min_cacheFileLocking = empty($CFG->preventfilelocking);
 $min_serveOptions['bubbleCssImports'] = false;
 $min_serveOptions['maxAge'] = 1800;
 $min_serveOptions['minApp']['groupsOnly'] = true;