[GTK][CMake] Forward missing headers on Darwin
Created attachment 416709 [details] Patch
Committed r271073: <https://trac.webkit.org/changeset/271073> All reviewed patches have been landed. Closing bug and clearing flags on attachment 416709 [details].
<rdar://problem/72630402>
spi/darwin/OSVariantSPI.h also needs to be forwarded.