[llvm] [extract_symbols.py] Add DATA flag for non-function export symbols (PR #101951)

[via llvm-commits]

shatyuka wrote:

It will affects the import library. The dll files are identical with or without DATA, but if you link your dll with the import library without DATA, you are expected to get a wrong `var` value, ending with 25FF in hex.
I'm compiling clang and plugin with clang toolchain, and link my plugin directly to clang.exe. So it's possible that the problem is only in this case. I haven't tested the msvc case, nor have I tried clang's import library.

https://github.com/llvm/llvm-project/pull/101951