cs go and bumblebee

# This does work
1/ Modify de launch script of cs go (~/.steam/steam/steamapps/common/Counter-Strike\ Global\ Offensive/csgo.sh):
${DEBUGGER} "${GAMEROOT}"/${GAMEEXE} "$@"
becomes
primusrun ${DEBUGGER} "${GAMEROOT}"/${GAMEEXE} "$@"

2/ Explicitly tell steam to launch that script and nothing else:
In the launch options of the game:
~/.steam/steam/steamapps/common/Counter-Strike\ Global\ Offensive/csgo.sh

3/ Bonus: disable vsync:
In the launch script, add this line:
export vblank_mode=0


# This does not work
$ steam &
$ LD_LIBRARY_PATH=~/.steam/bin32/ ~/.steam/bin32/steam-runtime/run.sh primusrun ~/.steam/steam/steamapps/common/Counter-Strike\ Global\ Offensive/csgo.sh
But there is no VAC then.