Create platform plugin binary into the local plugins directory.
Create platform plugin binary into the local plugins directory.

Set DESTDIR to $$QT.compositor.plugins/platforms in order to create
the plugin binary into the local plugins directory.  When building
Linux packages you usually are in a chroot environment and can't
write files outside your build directory, this change avoid
permission errors.

Change-Id: I3e518f20308b852f4de6a5355af60fc67681cace
Reviewed-by: Jørgen Lind <6105bb7d7ebdd613cef5835c4a38d29949bd95ac@nokia.com>

Tofee/qtwayland,Tofee/qtwayland,Tofee/qtwayland,ntanibata/qtwayland,locusf/qtwayland-1,ntanibata/qtwayland,locusf/qtwayland-1,ntanibata/qtwayland,locusf/qtwayland-1,locusf/qtwayland-1