MSBuild on windows currently spews a warning about buildinfo.h_fake not being generated. For build info we use a non existing file to trigger a custom_command on every build, which has worked well for years now, however in recent versions of MSBuild it has started issuing warnings about files that should be generated but are not. CMake is actually aware of this being a problem and states in the documentation that "If the output of the custom command is not actually created as a file on disk it should be marked with the SYMBOLIC source file property." This change fixes the build warning by properly marking the buildinfo.h_fake as symbolic resolving the warning.