llvm-tools on nightly doesn't package with external LLVM

[semarie]

since #51728, Rust failed to package properly when LLVM is configured as external dependency (with explicit llvm-config in config.toml)

  > LlvmTools { stage: 2, target: "x86_64-unknown-openbsd" }
Dist LlvmTools stage2 (x86_64-unknown-openbsd)

thread 'main' panicked at 'fs::File::open(&src) failed with No such file or directory (os error 2)', bootstrap/lib.rs:1194:25
stack backtrace:
   0: <std::ffi::c_str::NulError as core::fmt::Debug>::fmt
   1: <std::env::JoinPathsError as core::fmt::Debug>::fmt
   2: <std::ffi::os_str::OsString as core::fmt::Debug>::fmt
   3: <std::ffi::os_str::OsString as core::fmt::Debug>::fmt
   4: <std::ffi::os_str::OsString as core::fmt::Debug>::fmt
   5: <std::ffi::os_str::OsString as core::fmt::Debug>::fmt
   6: <std::ffi::os_str::OsString as core::fmt::Debug>::fmt
   7: <bootstrap::dist::LlvmTools as core::fmt::Debug>::fmt
   8: <bootstrap::dist::LlvmTools as bootstrap::builder::Step>::make_run
   9: <&'a T as core::fmt::Debug>::fmt
  10: <bootstrap::dist::Extended as bootstrap::builder::Step>::make_run
  11: <&'a T as core::fmt::Debug>::fmt
  12: <bootstrap::dist::Extended as bootstrap::builder::Step>::make_run
  13: <bootstrap::compile::Assemble as core::fmt::Debug>::fmt
  14: <bootstrap::compile::Assemble as core::fmt::Debug>::fmt
  15: <bootstrap::compile::Assemble as core::fmt::Debug>::fmt
  16: <bootstrap::compile::Assemble as core::fmt::Debug>::fmt
  17: <bootstrap::dist::LlvmTools as core::fmt::Debug>::fmt
  18: __register_frame_info
  19: __register_frame_info
  20: <std::ffi::os_str::OsString as core::fmt::Debug>::fmt
  21: <std::env::JoinPathsError as core::fmt::Debug>::fmt
  22: <std::io::error::Error as core::fmt::Display>::fmt
  23: __register_frame_info
  24: __register_frame_info
  25:
Traceback (most recent call last):
  File "/data/semarie/build-rust/build_dir/rustc-nightly-src/x.py", line 20, in <module>
    bootstrap.main()
  File "/data/semarie/build-rust/build_dir/rustc-nightly-src/src/bootstrap/bootstrap.py", line 827, in main
    bootstrap(help_triggered)
  File "/data/semarie/build-rust/build_dir/rustc-nightly-src/src/bootstrap/bootstrap.py", line 818, in bootstrap
    run(args, env=env, verbose=build.verbose)
  File "/data/semarie/build-rust/build_dir/rustc-nightly-src/src/bootstrap/bootstrap.py", line 148, in run
    raise RuntimeError(err)
RuntimeError: failed to run: /data/semarie/build-rust/build_dir/build/bootstrap/debug/bootstrap dist --jobs=4

the No such file or directory error is because buildrust tries to copy:
/data/semarie/build-rust/build_dir/build/x86_64-unknown-openbsd/llvm/bin/llvm-nm to /data/semarie/build-rust/build_dir/build/tmp/dist/llvm-tools-image/bin/llvm-nm.

But as LLVM was external, the directory build/x86_64-unknown-openbsd/llvm/ is empty.

I think there is two possibilities:

• doesn't package llvm-tools componment if LLVM is external
• package it, but uses the right directory

I will make a PR if someone told me the direction to take.

[Mark-Simulacrum]

I think we should probably package it, cc @japaric @alexcrichton

[alexcrichton]

I'd personally err on the side of skipping it, if we try to package it we're gonna have to deal with a whole array of local installs and filenames, and it's not actually used anyway