[llvm] [ORC-RT] Initial check-in for a new, top-level ORC runtime project. (PR #113499)

[Chris B via llvm-commits]

llvm-beanz wrote:

> Having done a bit more reading, and chatting with @etcwilde, it looks like `llvm-project/runtimes` is for single target builds and we expect some higher level script to invoke this for each target.

Runtimes when included as the top-level CMake file is a single configuration, when included from LLVM it is multi-configuration. LLVM's build manages the multi-invocation. The [Fuchsia toolchains](https://github.com/llvm/llvm-project/blob/main/clang/cmake/caches/Fuchsia-stage2.cmake) build multiple targets using the runtimes build, and is a good example for the setup.

> Using `llvm-project/llvm` as the source project gets us some kind of multi-target support, but I'm struggling to hold it right: Ideally I want to be able to do a multi-target build of orc-rt with either the host compiler or the just-built compiler, depending on config. Is that doable with the existing CMake machinery?

The existing runtimes build is designed to only support building the runtimes with the just-built compiler, so it does not support multi configuration building with the host compiler.



https://github.com/llvm/llvm-project/pull/113499