Use function attribute "frame-pointer" instead of "no-frame-pointer-elim"
LLVM 8 ([D56351](http://reviews.llvm.org/D56351)) introduced "frame-pointer". In LLVM 10 (D71863),
"no-frame-pointer-elim"/"no-frame-pointer-elim-non-leaf" will be
ignored.
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In the LLVM monorepo, run `git show origin/release/8.x:llvm/lib/CodeGen/TargetOptionsImpl.cpp` to see that `"frame-pointer"` is available since LLVM 8.