If you only need selected ones, you could have the build process show the invocations and just rerun them with additional flags…

Actually I also tried that, but then I found that searching for the correct invocation and massaging it is not as convenient as I hoped. (Maybe I’m not very good with CMake.)  For one thing, those nvcc arguments are huge and easily span a dozen lines in my editor. 
Well, if I had to do it every five minutes, then I’d probably try and find a way to automate it, because “re-building the whole PyTorch with a different argument” takes more time than that.  On the other hand, I could use some coffee break!