package/opencv3: fix build for x86_64 target

This change backports a fix from upstream fixing missing symbols due to
wrong compiler optimization flags.

On Buildroot side, also remove deprecated options passed on the
configure command.

Fixes:
  http://autobuild.buildroot.net/results/af950c6172a578c4eeeb9440b6990ceb48263fa6/
  http://autobuild.buildroot.net/results/e8832302cd4f30cec076f67965f6aacbaca5b955/



Cc: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Signed-off-by: Samuel Martin <s.martin49@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>