fix broken assimp usage on windows
fix broken assimp usage on windows

VCPKG changed the layout of the CMake file from assimp.
Earlier ASSIMP_LIBRARIES_RELEASE pointed to the release library.
Now the variable does not exists anymore and ASSIMP_LIBRARIES leverage
the usage of CMake build in optimized/debug options. With this patch
IPPP is able to build with latest version of vcpkg.

Signed-off-by: Tobias Kohlbau <059b8b880f8441509ec8a65b50b4c6ae74ebea76@kohlbau.de>

SaschaKaden/RobotMotionPlanner,SaschaKaden/RobotMotionPlanner