mingw: Fix FindOpenVDB
mingw: Fix FindOpenVDB

Signed-off-by: Mehdi Chinoune <08b1b5066d15debe5d520804537f768887925fd1@hotmail.com>

dreamworksanimation/openvdb,dreamworksanimation/openvdb,dreamworksanimation/openvdb,dreamworksanimation/openvdb