CPack/NSIS: Document and check requirement of at least NSIS 3.0
Since !4171 (merged) we require NSIS 3.0. Since older versions do not support Windows 8 or above, we can now require at least version 3.0.
Fixes: #20514 (closed)
Backport: release
Since !4171 (merged) we require NSIS 3.0. Since older versions do not support Windows 8 or above, we can now require at least version 3.0.
Fixes: #20514 (closed)
Backport: release