EXPERIMANTAL: -fstack-protector-strong

docker/Dockerfile.build.ubuntu20

@@ -42,6 +42,6 @@ RUN /bin/sh oaienv && \
       -w USRP -t Ethernet \
       --build-e2 --cmake-opt -DXAPP_MULTILANGUAGE=OFF \
       --noavx512 \
-      --cmake-opt -DCMAKE_C_FLAGS=-Werror --cmake-opt -DCMAKE_CXX_FLAGS=-Werror $BUILD_OPTION && \
+      --cmake-opt -DCMAKE_C_FLAGS="-Werror -fstack-protector-strong" --cmake-opt -DCMAKE_CXX_FLAGS="-Werror -fstack-protector-strong" $BUILD_OPTION && \
     # Mainly to see if the sanitize option was perfectly executed
     ldd ran_build/build/nr-softmodem