Bump version to 6.12.0


Change-Id: I4bd8fe158041444ea6e82f8cf4f0c73001ffa76b
Reviewed-by: Akseli Salovaara <akseli.salovaara@qt.io>
commitdc3f0a72ec78daf86efd7a1aa59143e313ed3722
parent29af82a1f3a1f236e759b0faa6f0d26b3294d0a2
authorJani Heikkinen <jani.heikkinen@qt.io>
committerJani Heikkinen <jani.heikkinen@qt.io>
commit timeTue, 16 Dec 2025 22:48:12 +0000