Coming from the word "Rasha" meaning "bad or "evil". "Ersha" is the future tense of "rasha", so Iyov is saying:
"It is in your knowledge (you know) that I will not do evil (i.e. - become evil or wicked)..."
I'd like to know how Chabad's translation of "become condemned" fits in, here. That seems to imply a "passive" verb, and I don't see this definition coming directly from the word "ersha". I'd appreciate some insight to Chaba"d's translation.
In viewing the Gemarah source that you refer to, see Rashi's translationon that page. It seems that Iyov was attempting to provide a valid "excuse" that humanity could use for being absolved of G-d's judgement, because He created the Yetzer Hara (evil inclination), and thus, everyone is an "ones" (someone who couldn't control the situation). Thus, (according to Rash"i) Iyov was stating, "If you (G-d) had wanted, I would not have been evil".