Select CMake cURL version to build with

CMake uses the bundled cURL library by default. When debugging connectivity issues with CMake, a developer may wish to build CMake with a specific cURL version. To do so, from the cmake/ project source directory, use options like:

cmake -Bbuild -DCURL_ROOT=/path/to/curl -DCMAKE_USE_SYSTEM_LIBRARY_CURL=yes

Then build CMake as usual.

Verify the Curl version used with this script.