cmake: Add version 3.16.3 (#18034)
cmake: Add version 3.16.3 (#18034)

`cmake @3.16.3` is the version provided by Ubuntu 20.04. Adding this version here avoids the warning
```
==> Warning: Missing a source id for cmake@3.16.3
```
when using the system `cmake`.
iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack,LLNL/spack,LLNL/spack,iulian787/spack,LLNL/spack,iulian787/spack