First, and foremost--
You are using an unofficial PCSX2 build.
Those are not supported here on the official forums,
unlike
Official SVN builds.
But since I'm sure you'll switch over,
I'll good ahead and help you with your system's issue.
Although-- maybe you would encounter less issues with official software...
There should be settings relating to Optimus in the nVidia Control Panel, I believe.
Whether it's appliable globally (always use dedicated GPU),
or just specifying certain programs to use eith the integrated or dedicated unit;
I'm sure there was something in there for that.
If not-- Consider updating your nVidia software.
If the option is in your PC's BIOS,
that would be the ultimate override.