TYPO3 Core

Since commit https://review.typo3.org/c/54020/ + followup https://review.typo3.org/54061 (released only in v9) it is no longer possible to configure the 'assets' cache in ext_localconf.php files.

The IconRegisty is loaded in backend mode and reads the configuration (caches from 'assets') during object construction.
IconRegistry is usually instantiated during ext_localconf.php (due to extensions registering icons),
and therefore create's the 'assets' cache during ext_localconf.php loading.

After CacheManager has created the assets cache once, it will never be recreated again,
when the final configuration is set, after all ext_localconf.php files have been loaded.