A way to out-put building self-contained deps

[weihanglo]

Summary

Posted by @denizsokmen #141375 (comment):

Custom target issue is actually more related to Rust bootstrap forcefully cross-compiling crtbegin, crtend and llvm-libunwind for musl for self-contained linkage reasons:

rust/src/bootstrap/src/core/build_steps/compile.rs

Line 422 in 40ace17

let libunwind_path = copy_llvm_libunwind(builder, target, &libdir_self_contained);

and https://github.com/rust-lang/rust/blob/master/src/bootstrap/src/core/config/target_selection.rs#L96

I see no way to opt out of that, even though those binaries won't be used as they'll be fetched from the sysroot of that musl-based custom target. Is there a way to tell Rust bootstrap not to bother with preparing self-contained binaries?

Expected behaviour

A way to out-put crtbegin, crtend and llvm-libunwind build for custom musl target.

Actual behaviour

You'll need to patch code as described: #141375 (comment).

Possible solution

Probalby extend the target table in bootstrap.toml like target.self-contained = <bool>?

Bootstrap configuration (bootstrap.toml)

[target.my-custom-musl]
linker = "…"
musl-root = "…"
cc = "…"
cxx = "…"
cflags = "…"
cxxflags = "…"
rustflags= "…"
llvm-libunwind = "system"

HEAD

5b9007b