oeqa/runtime/context.py: Fix use of getTarget() with testexport
The idea on getTarget is to use kwargs to send custom variables
to different targets, instead of this, a new variable was added
(just used for custom targets) and this broke testexport. So
in order to fix it, just add the custom variable to kwargs.
This fixes the use of getTarget() in testexport class that was
introduced in
1dc8010afd71fe46fb28bb86fb7c07a5fbd3d7cf.
Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
