[Backport v4.0.99-ncs1-branch] [nrf fromlist] boards: nordic: Add sysbuild for NS boards#2772

carlescufi merged 2 commits intov4.0.99-ncs1-branchnrfconnect/sdk-zephyr:v4.0.99-ncs1-branchfrom

backport-2768-to-v4.0.99-ncs1-branchnrfconnect/sdk-zephyr:backport-2768-to-v4.0.99-ncs1-branchCopy head branch name to clipboard