Over being asked "Will this work to measure the thing?" The character answers this:
知らねえ!
測れてりゃいい 測れてりゃ
Will the first one seems to be a ばいい, I'm unsure on how the second one is being used. Is it some kind of grammar? The meaning I get seems to be "If you want to measure it, just measure it"?
Both instances of 測れてりゃ are the eba-to-ya contracted form of 測れてれば, which is a combination of 測れる for potential, て(い)る for perfect aspect, and ば for the conditional. There is no meaning of "wanting to". Both mean "if you've (successfully) measured it". This has nothing to do with any special grammar rule. Simply, the conditional part was said twice for emphasis.
測れてりゃいい 測れてりゃ
If you've measured it, that's fine — as long as you've measured it!
I need a little more context, but this person might be suggesting that accuracy is not important as long as there is a measurement result.
"If you want to measure it, just measure it" would be something like 測りたきゃ測りな.
