package/opencv3: fix build with gcc bug 64735

OpenCV3 allows to disable the usage of std::exception_ptr:
https://github.com/opencv/opencv/issues/11878#issuecomment-402099255

Fixes
http://autobuild.buildroot.net/results/5ca/5ca221792c72c0a19f8b0e8303c0603d28f3c48e/



Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>