Fix android build issues

code/D3MFOpcPackage.cpp

@@ -49,6 +49,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <assimp/DefaultLogger.hpp>
 #include <assimp/ai_assert.h>
 
+#include <cstdlib>
 #include <memory>
 #include <vector>
 #include <map>