CMake: Make benchmarks buildable standalone


Add the necessary project file stanza that allows to configure the
benchmarks with qt-cmake-private.

Change-Id: I3f3aa5164849d38ee1ccfd2146d4af1830026a55
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
commit7216392185dc4b2999fe42b2f45ae924aad92924
parent0dbc76768d701d90f9c3a66803b5b048e6d18b93
authorJoerg Bornemann <joerg.bornemann@qt.io>
committerJoerg Bornemann <joerg.bornemann@qt.io>
commit timeWed, 30 Sep 2026 13:34:04 +0000