libspatialindex: fix build on Microblaze

This commit fixes the build of libspatialindex on the Microblaze
architecture by working around a gcc bug, by passing -O0 as the
optimization level.

A patch to configure.ac is needed to not have -O2 be forced by the
libspatialindex build system, and therefore AUTORECONF=YES is now
needed.

Fixes:

  http://autobuild.buildroot.net/results/bbba2a2c97dbec21340c7fd07162a316a411cba4/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>