Averting excessive oopses

Yes, specifically make LLVM=1 with the full-lto option on llvm 15, x86-64. Happening over a few weeks, my working theory was that the power supply was getting marginal with age. Then on a whim I made the next update plain GCC and it's been fine ever since.

There's good reasons why that code is impossible to activate by accident, so I can't complain too much.