workaround stack bashing by asm on 32-bit OpenBSD

like Darwin, disable x86inc with 32-bit PIC/shared library builds;
avoids stack smashing done by vp9_subpixel_*

workaround for issue #808

Change-Id: I3f2f16bd91822c8e8dad0242b5dcfb0e621aea97
1 file changed