Bump version to 6.12.0


Change-Id: I5958979a972e4b53b0a7e356551b4890f2eaae52
Reviewed-by: Akseli Salovaara <akseli.salovaara@qt.io>
commit4c732a6a6da9b8f4433217d3d38fb71c4f1da78d
parentd312c4007e524a1c3990c029b4febba575dad3d5
authorJani Heikkinen <jani.heikkinen@qt.io>
committerJani Heikkinen <jani.heikkinen@qt.io>
commit timeTue, 16 Dec 2025 21:03:25 +0000