Rust: libunwind contained in rust-src won't build for some targets

[iulianR]

Describe the problem you are trying to solve

When trying to build Rust std, I came across this problem for target aarch64-unknown-linux-musl. The llvm-project directory does not exist in the rust/src directory and libunwind won't build due to that. @RalfJung might have pinned the problem down to a PR. The llvm-project directory is required to build libunwind and for the Rust project is provided as a submodule.

Describe the solution you'd like

@RalfJung thinks a solution might be adding the llvm-project directory to the list of src paths that will make into the rust-src component, but it is not clear if that's the right solution. I am also not sure that's the right way as the directory is quite large.

Notes

Sorry if I might have misinterpreted your words, @RalfJung, I did not intend to. Thanks!

[RalfJung]

a solution might be adding the llvm-project directory to the list of src paths that will make into the rust-src component

Correction: just llvm-project/libunwind should be needed.