wrong flags in linux travis build script

Former-commit-id: 08f4984dbfc1fac85c8d6990b95f185f83a1273b

.travis.yml

@@ -17,7 +17,7 @@ matrix:
         - cd tutorial
         - mkdir build
         - cd build
-        - cmake -DLIBIGL_USE_STATIC_LIBRARY=ON -DCMAKE_CXX_COMPILER=g++-4.8 -DCMAKE_C_COMPILER=gcc-4.8 -DLIBIGL_WITH_EMBREE=OFF ../
+        - cmake -DLIBIGL_USE_STATIC_LIBRARY=ON -DCMAKE_CXX_COMPILER=g++-4.8 -DCMAKE_C_COMPILER=gcc-4.8 ../
         - make -j 2
       addons:
         apt: