Building rustc-1.84.0 tarball fails when using system LLVM

[debohman]

I have LLVM 19.1.6 installed on my system, and when building, I encounter the following:

Dist rust-std-1.84.0-x86_64-apple-darwin
	finished in 0.534 seconds
Installing stage2 std (x86_64-apple-darwin)
install: creating uninstall script at /tmp/dst.rustc/usr/local/lib/rustlib/uninstall.sh
install: installing component 'rust-std-x86_64-apple-darwin'

    rust std installed.

thread 'main' panicked at src/lib.rs:1708:24:
src.symlink_metadata() failed with No such file or directory (os error 2) ("src = /tera/tera/debo/Projects/rustc/rustc-1.84.0-src/build/x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/bin/llvm-objcopy")
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
Build completed unsuccessfully in 0:29:14

It appears that it is trying to invoke a built copy of llvm-objcopy, when it should be using the installed version.

This is a regression.

[debohman]

The commit that is causing the build to blow up is d8ab230e731ea0bcaf299b86e82558f354f8e2b0:

commit d8ab230e731ea0bcaf299b86e82558f354f8e2b0
Author: David Wood <david@davidtw.co>
Date:   Tue Oct 8 15:19:37 2024 +0100

    bootstrap: include `llvm-objcopy` in dist

There seems to be other work involved in this that I have not identified yet. This scheme needs to be conditional based on whether we are building and also installing the llvm tools.

Note that I have the following in my config.toml:

llvm-tools = false

[jieyouxu]

The problem is that the compiler unconditionally expects llvm-tools to be available (specifically llvm-objcopy to workaround some nasty macOS strip problems). I gated this on (1) llvm being enabled and (2) llvm-tools being enabled in #132720, but we expect this to be available in both dist and compile flows as implemented in #131405.

When you disable llvm-tools in config.toml, we probably need to require that system llvm-tools could be found and a system llvm-objcopy is copied instead, probably by querying system llvm-config.

[debohman]

Okay, but if we are not building LLVM and hence not installing the llvm-tools, then it seems to me that we should be creating a symlink from the installed llvm-objcopy to rust-objcopy for the compiler.

[onur-ozkan]

#134240 fixes that, but it's not on stable yet.

[debohman]

I made an error in my previous comment. The correct behavior is to copy the system llvm-objcopy to rust-objcopy in the destination root.