Merge topic 'presets-build-fixes' into release-3.20

534c40e6d8 presets: Fix buildPreset "targets" not allowing a single string
5d67632813 presets: Fix buildPreset "jobs"
93e396b402 presets: Fix buildPreset "jobs" field test case

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Kyle Edwards <kyle.edwards@kitware.com>
Merge-request: !6190