I am wondering about using the GUI installer for installing Gentoo 2008.0. I know that is uses rather generic USE flags and CFLAGS, and I would much rather have them set manually myself. However, I here that I can use emerge world (with some option I don't remember) to reread the USE flags after the install. But I don't know if the same is true for the CFLAGS. In particular, I'd like to set my "march" myself, as I hear that noticeable performance benefits can result. Is there a way to rebuild the whole system with a new "march"? Otherwise I think I'd want to manually install.
Thanks!

