The policy CMP0074 has been switched to a new behavior, which removes the CMake warning about the use of _ROOT variables.
Some useful definitions have been added for building on Windows, in particular, this removes the warning about _WIN32_WINNT during compilation.
3. Using build targets instead of library paths eliminates the error if CURL was not found.
Do not link CURL if it is not found. This eliminates a CMake error if someone is not using the optional CURL.
3. Using build targets instead of library paths eliminates the error if CURL was not found.