Fix permissions in installed Qt5 header files

For the qt5-* ports bsd.qt.mk sets EXTRACT_AFTER_ARGS, and
thereby does not get the normal default value of

--no-same-owner --no-same-permissions

passed when extracting. This lead to for example header files
being installed (i.e. copied), with permissions group write
permissions.

Manually append that to the bsd.qt.mk shenanigans (also do the
same in www/qt5-webchannel, which opts out of the bsd.qt.mk value)

PR: 227027
Reported by: grarpamp@gmail.com