message: ci: use GCC 8 when building packages in native_qt5 CI
  Our minimum required GCC is GCC 8, and this change in required for
  changes like which take advantage of flags introduced in that
  version of GCC.
  This should have been included as part of
diff: @@ -9,7 +9,7 @@ export LC_ALL=C.UTF-8
  export CONTAINER_NAME=ci_native_qt5
  export DOCKER_NAME_TAG=ubuntu:18.04 # Check that bionic gcc-8 can compile our C++17 and run our functional tests in python3, see doc/dependencies.md
  export PACKAGES="gcc-8 g++-8 python3-zmq qtbase5-dev qttools5-dev-tools libdbus-1-dev libharfbuzz-dev"
  -export DEP_OPTS="NO_QT=1 NO_UPNP=1 NO_NATPMP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1"
  +export DEP_OPTS="NO_QT=1 NO_UPNP=1 NO_NATPMP=1 DEBUG=1 ALLOW_HOST_PACKAGES=1 CC=gcc-8 CXX=g++-8"
  export TEST_RUNNER_EXTRA="--previous-releases --coverage --extended --exclude feature_dbcrash" # Run extended tests so that coverage does not fail, but exclude the very slow dbcrash
  export RUN_UNIT_TESTS_SEQUENTIAL="true"
  export RUN_UNIT_TESTS="false"
  