fix parallel installation of private and qpa headers in qt framework bundles

with qmake now de-duplicating the paths properly, we should version
these QMAKE_BUNDLE_DATA entries as well, so we don't depend on the
symlinking of the regular headers being done first.

Change-Id: Idaa2ccc1ba9b5684b0c8d84f7f760735f54432e1
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>