qt6_tool: Use Qt keys for unity builds


Adapt to qtbase/ed26352a1009ce37fe792c023af9e5d6259ea6d4.

Change-Id: I8cd7a51c5bd998ab56914b97b2044e4cbacdad20
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
commit7a3a23f3ccd74c0a1041ee244f48b4e6b0c72ba6
parent3f7865c20ee89ba9f00b62699c7a21e180172936
authorFriedemann Kleint <Friedemann.Kleint@qt.io>
committerFriedemann Kleint <Friedemann.Kleint@qt.io>
commit timeMon, 8 Sep 2025 08:52:35 +0000