By definition, vegans do not use any animal product, food or otherwise
Veganism is a way of living which seeks to exclude, as far as is possible and practicable, all forms of exploitation of, and cruelty to, animals for food, clothing or any other purpose.
Although I know many Vegans, I do not personally know any Vegan that would condone "lab grown meat that used fetal calf serum" or support PETA's position on this topic.
Although there may be an exception, I am going to say the consensus opinion would be to avoid any use of any animal product, including "lab grown meat that used fetal calf serum".
If it took killing to produce, I wouldn't eat it. That would go against my morality.
However, there is also the bigger picture here. Millions of animals die everyday just for the consumption of their flesh. If one calf being killed is going to stop many more from not being killed, I can understand why a group dedicated to animal welfare would support it.
That said, there are other groups/companies that are making "lab grown meat" without killing, though they still do initially involve at least taking muscle from living animals as far as I know.