CMake error following build instructions

Using instructions here: https://github.com/getdnsapi/getdns#building
Using cmake version 3.25.0:

```
cmake .
```
Aforementioned command results in:

```
CMake Warning:
  Ignoring extra path from command line:

   "."


CMake Error: The source directory "/" does not appear to contain CMakeLists.txt.
Specify --help for usage, or press the help button on the CMake GUI.
```