New in version 3.23.
Semicolon-separated list of files in the target's
<NAME> header set,
which has the set type
HEADERS. If any of the paths are relative,
they are computed relative to the target's source directory. The property
This property is normally only set by
rather than being manipulated directly.
HEADER_SET for the list of files in the default header set.
HEADER_SETS for the file set names of all header sets.