Unity: Don't include sources with HEADER_FILE_ONLY property set
Replaces !4018 (closed)
Fixes: #19946 (closed)
Fixes: #19947 (closed)
Backport: release
Edited by Craig Scott
Replaces !4018 (closed)
Fixes: #19946 (closed)
Fixes: #19947 (closed)
Backport: release