SYMBOLIC

Is this just a name for a rule.

If SYMBOLIC (boolean) is set to True the build system will be informed that the source file is not actually created on disk but instead used as a symbolic name for a build rule.

© 2000–2020 Kitware, Inc. and Contributors
Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.17/prop_sf/SYMBOLIC.html