What do you mean, new? LTO has been in GCC since 2011. It's old enough to have a social media account in most jurisdictions.
I will just throw in some nostalgia for how good that compiler was. My college roommate brought an HP pizza box that his dad secured from HP, and the way the C compiler quoted chapter and verse from ISO C in its error messages was impressive.
The idea of optimizations running at different stages in the build, with different visibility of the whole program, was discussed in 1979, but the world was so different back then that the discussion seems foreign. https://dl.acm.org/doi/pdf/10.1145/872732.806974