Add support for specifying CPS's supplemental `description` and
`website` attributes. Add ability to inherit these from the `project()`,
similar to how version information can be inherited.
Modify {export,install}(PACKAGE_INFO) commands to inherit version
information from the current project in situations where it seems
reasonable to do so. Add an option to explicitly request inheritance
from a specific project.
This leverages the recently added project(COMPAT_VERSION).
Add import/export support and documentation for the SPDX_LICENSE
target property. A target's license can be specified by setting
this property to an SPDX license expression. CMake and CPS-format
export files generated with `export()` or `install()` will
retain the license information. CMake also imports the license
property for imported targets.
Closes: #26706
Matthew Woehlke