[llvm] Reland [CGData] llvm-cgdata #89884 (PR #101461)

[Kyungwoo Lee via llvm-commits]

kyulee-com wrote:

> Why isn't this just put inside llvm/tools/llvm-cgdata/lib ? See llvm/tools/llvm-exegesis for an example of the lib being separated from the tool.

This library is not exclusively used by the `llvm-cgdata` tool; it can be also used in LLD or ThinLTO. As detailed in the discussion on RFC: https://discourse.llvm.org/t/rfc-enhanced-machine-outliner-part-2-thinlto-nolto/78753, this library will be invoked from LLD (see this [commit](https://github.com/llvm/llvm-project/pull/90166/commits/0b026f309b8eacd3790f3ab58d3b114b9e70cad0)) or ThinLTO (refer to this [commit](https://github.com/llvm/llvm-project/pull/90933/commits/fa5ea89232740fa3e405460512b7aa2c2b5dc343)). So, I think placing it inside `llvm/tools/llvm-cgdata/lib` would limit its accessibility across different clients.

https://github.com/llvm/llvm-project/pull/101461