- `-fomit-frame-pointer` is included automatically by both GCC and
Clang in `-O1` and above.
- `-ftree-vectorize` is included automatically by GCC in `-O2` and
beyond, and seems always enabled by Clang.
Closes#66296. See that issue for a detailed investigation.
(cherry picked from commit c5c3d13dc0dbbf95a2350f57d69e7cdc546d395d)