libtorch_cpu.so is exposing some LLVM symbols

[sanchitintel]

🐛 Describe the bug

#63272 had hidden LLVM symbols by making LLVM a PRIVATE dependency of torch_cpu in caffe2/CMakeLists.txt, but libtorch_cpu.so is still exposing some LLVM symbols.

nm -D ./build/lib/libtorch_cpu.so | grep llvm
000000000ca82122 B FLAGS_torch_jit_llvm_use_fast_intrinsics
0000000009fe4650 T llvm_orc_deregisterEHFrameSectionWrapper
0000000009fe4720 T llvm_orc_registerEHFrameSectionWrapper
000000000a048800 T llvm_regcomp
000000000a049120 T llvm_regerror
000000000a04bba0 T llvm_regexec
000000000a04cfb0 T llvm_regfree
000000000a04d030 T llvm_strlcpy

This issue doesn't affect PyTorch directly but can affect a PyTorch C++ extension if it links to another library that also links to LLVM.
Even in that case, workarounds can be used, so it's probably not a high priority issue at this point. Thanks!

Versions

Master branch

cc @malfet @seemethere @zou3519 @ZhennanQin