Introduced llvm-libtool option

[catap]

An idea to allow to control used libtool to build LLVM. Useful in attmept to build / bootsrap rust to old or wired systems.

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @Mark-Simulacrum (or someone else) soon.

Please see the contribution instructions for more information.

[Mark-Simulacrum]

Is this environment variable standard (e.g., read by cmake itself or something?) -- otherwise, I would prefer that if it needs to be configured, we do so via config.toml rather than an ad-hoc environment variable.

[catap]

@Mark-Simulacrum nope, it isn't a standard environment variable. Let me move to config when.

[catap]

@Mark-Simulacrum like this?

[Mark-Simulacrum]

Can you say more about the motivation for this? It looks like the intent is to use it to bootstrap on old (and no longer supported) systems, but there I would expect that you can place libtool in PATH and that should work well?

Since such systems will likely need a bunch of other patches applied to the rustc src tree anyway to enable successful builds, it's not clear to me this adds value -- and exposing an option generally not used seems like it adds complexity for all users, so I would prefer to avoid doing so.

[catap]

@Mark-Simulacrum yes, you're right that I'm trying to make rust works on old system. In my case it is macOS 10.6.

My goal is quite simple: bring rust to old macOS via MacPorts. MacPorts provides a lot of modern software to old system which includes modern clang :)

Why? Because rust is starting to be popular platform to write new software. For example mozjs.

Right now I've bring a bit old rust (1.42) to macOS 10.6 and I'm just bootstrapping it one-by-one, it requires some time :)

Patch? Yes, I needed it but it is releativle small. Differences with rustc-1.42.0-src is:

24 files changed, 125 insertions(+), 15 deletions(-)

[Mark-Simulacrum]

My sense is that if you need to adjust a bunch of llvm building opts, it probably makes sense to build llvm out of tree and specify it with llvm-config - that'll let you configure more freely, and without as much pain trying to pipe options through here.

[Mark-Simulacrum]

I'm going to close this in favor of #93756. Thanks!