CMake: Make benchmarks buildable standalone


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

Change-Id: Ia4334e2dbecd7a834f5e21fcd8db6476a451334a
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>
commitf03f954bf5211f1fc9051f7c32d5655bbcf02646
parent75142dd8ceed17ec8bcf6181aa360614a5c96efe
authorJoerg Bornemann <joerg.bornemann@qt.io>
committerJoerg Bornemann <joerg.bornemann@qt.io>
commit timeWed, 30 Sep 2026 13:33:59 +0000