[llvm] [Runtimes] Merge 'compile_commands.json' files from runtimes build (PR #116303)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

> Have you measured at the performance on larger builds? For example, in the [Fuchsia toolchain build](https://github.com/llvm/llvm-project/blob/d681e1030ffd71412294d3fadc7ef673f822b832/clang/cmake/caches/Fuchsia.cmake) that I normally use, I have 38 `compile_commands.json` files, the top-level one is 12M and the individual runtime ones are around 1-2M. Python is not the fastest language out there and I just want to make sure this doesn't become a bottleneck even for larger builds.

My build has three, but I'm on a beefier server. I'd assume someone doing a standard release build might turn off the compile commands if they don't want the overhead? Would it be possible for you to try it locally? It'd be hard for me to test Fuchsia's build locally. I didn't notice any considerable slowdown, and it only happens once per reconfigure so rebuilds are fast for the most part.

https://github.com/llvm/llvm-project/pull/116303