Update build_on_demand.yml

Author: Sygmei

.github/workflows/build_on_demand.yml

@@ -42,6 +42,9 @@ jobs:
     - name: Compile ObEngine
       working-directory: ./obengine
       run: cd build; cmake -DBUILD_TESTS=ON -DBUILD_TOOLKIT=ON -DCMAKE_BUILD_TYPE=Release ..; make -j8
+      env:
+        CC: gcc-10
+        CXX: g++-10
     - name: Run tests
       working-directory: ./obengine
       run: LD_LIBRARY_PATH="$LD_LIBRARY_PATH;/usr/local/lib" ./build/tests/ObEngineTests