webos_qmake5: Fix EXPORT_WEBOS_QMAKE_MACHINE

* all recipes which were depending on this functionality were also
  setting WEBOS_QMAKE_TARGET, so I haven't noticed this copy&paste
  issue until now

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: Ic5c9f3072cd32e5af57df1b178221c63a358bc32
Reviewed-on: https://g2g.palm.com/2183
Reviewed-by: Build Verification <
;
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Reviewed-by: Martin Jansa <Martin.Jansa@lge.com>
Tested-by: Martin Jansa <Martin.Jansa@lge.com>
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Susan Montooth <susan.montooth@lge.com>