Moved `add_subdirectory(meson)` to the correct section

1 job for 5.4 in 60 minutes (queued for 53 minutes and 12 seconds)
Status Job ID Name Coverage
  Build
failed #13959
linux stable-kf5-qt5 qt5.12

01:00:00

 
Name Stage Failure
failed
linux stable-kf5-qt5 qt5.12 Build The script exceeded the maximum execution time set for the job
        Start  75: test_lldbformatters
kf5.kinit.klauncher: new app ":1.41"
kf5.kinit.klauncher: new app "org.kdevelop.kdevplatform-lock-f595388f-24b7-4202-88ad-0c5b909ea3ce"
75/121 Test #75: test_lldbformatters ..................... Passed 8.08 sec
Start 76: test_gdb
kf5.kinit.klauncher: new app ":1.42"
kf5.kinit.klauncher: new app "org.kdevelop.kdevplatform-lock-de0d3fb3-1526-4900-be87-8d984457c59c"
Pulling docker image gitlab/gitlab-runner-helper:x86_64-ac2a293c ...
ERROR: Job failed: execution took longer than 1h0m0s seconds