[cfe-dev] [CMake][ELF] Add -fno-semantic-interposition and -Bsymbolic-functions

[Fangrui Song via cfe-dev]

Motivated by a recent rant on too slow clang (linking against libLLVM.so and libclang-cpp.so)
when building the Linux kernel, I just created a CMake patch https://reviews.llvm.org/D102090
which will add -fno-semantic-interposition and -Wl,-Bsymbolic-functions to our build.
(My x86 kernel defconfig build is at least 15% faster)

I have added some distribution packagers as reviewers. Sending this message to
attract more users.