Image Builder not functional in v12

[mmalisz]

Due some changes to the TYPO3's core: v12 vs v11, the class GifBuilder causes crashes.

The problem is that in v12, the absolute path is passed to the output() method:
$this->output(Environment::getPublicPath() . '/' . $gifFileName);,
which with combination with the EXT returning the absolute path as well, the filename passed to the output() method looks like this: /var/www/html/public//var/www/html/public/var/transient/actual_filename.jpg, which will cause the exception being thrown.

[franzkugelmann]

I can confirm the issue.