fix optimization_spectrahedra example (#344) #1387

Set up job

Run actions/checkout@v1

Run sudo apt-get update || true; sudo apt-get install g++-9 lp-solve libopenblas-dev; rm -rf build; mkdir build; cd build; cmake -D CMAKE_CXX_COMPILER=g++-9 -D DISABLE_NLP_ORACLES=ON -D USE_MKL=OFF ../test; make; ctest --verbose;