3p: poly2tri compile fix


poly2tri requires an additional include when building with libc++ /
_LIBCPP_REMOVE_TRANSITIVE_INCLUDES

Pick-to: 6.12
Change-Id: I88c82e5e46a3587d806ae7ee283ecc0dd0d1e96c
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
commit48f947ad28abb2744dd2322710c3b9be976596c2
parent482d008f1b76d5b0451fe1cb24705020918baa45
authorTim Blechmann <tim.blechmann@qt.io>
committerTim Blechmann <tim.blechmann@qt.io>
commit timeTue, 20 Oct 2026 10:41:28 +0000