Enabling Link time optimization (LTO) with rpmbuild is one of the new features of Fedora 33. I read the changeset page once and went back only after I did the Tor package builds locally.

While building the package, I noticed that suddenly there are many processes with /usr/libexec/gcc/x86_64-redhat-linux/10/lto1 and my load average reached 55+. Here is a screenshot I managed to take in between.