CMake: add cmake specific .gitignore


Pick-to: 6.11
Change-Id: I75fc9ddac0f80636491824c6ee05261b1b18f099
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
commit68a99b285c03c24f484b084c8eb08aa8bbf67cb0
parentc61c8f1a05530081ff73e5207b3db758c9465635
authorAssam Boudjelthia <assam.boudjelthia@qt.io>
committerAssam Boudjelthia <assam.boudjelthia@qt.io>
commit timeTue, 14 Apr 2026 14:50:54 +0000