Tracking Issue for fine-grained `-C link-self-contained`

This is a tracking issue for the unstable parts of the command line option -C link-self-contained=+component1,-component2.
There's no RFC, but some of the feature was stabilized by an FCP for LLD-by-default.

The stable subset is documented in https://doc.rust-lang.org/rustc/codegen-options/index.html#link-self-contained.
The unstable and mostly unimplemented subset is documented in https://doc.rust-lang.org/beta/unstable-book/compiler-flags/codegen-options.html#link-self-contained.

About tracking issues

Tracking issues are used to record the overall progress of implementation.
They are also used as hubs connecting to other relevant issues, e.g., bugs or open design questions.
A tracking issue is however not meant for large scale discussion, questions, or bug reports about a feature.
Instead, open a dedicated issue for the specific matter and add the relevant feature gate label.
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Steps

• Support other components besides linker in rustc_codegen_ssa and maybe other places
• Move all the libraries and binaries to subdirectories of the self-contained directories corresponding to the individual components
• Move self-contained components not currently living in the self-contained directories to those directories
  • Move libunwind
  • Move mingw linker and C compiler
  • Move sanitizers
• Migrate targets using some shipped components without considering the self-contained mechanism to that mechanism
  • libunwind on some targets
  • linker and C compiler on mingw
  • sanitizers everywhere
• Migrate bare-metal targets using rust-lld as linker to using ld.lld through the self-contained mechanism
• On targets where -C link-self-contained=+something/yes does nothing it should be prohibited or unstable
• On targets where -C link-self-contained=-something/no does nothing and the target behaves correctly with regards to self-contained (rust-lld/libunwind/etc are migrated), it can be allowed and stabilized.
• On targets where -C link-self-contained doesn't behave correctly (rust-lld/libunwind/etc are not migrated), it should be prohibited or unstable
• On targets where -C link-self-contained=something does something it can be allowed and stabilized through an FCP or MCP mechanism
• Perhaps rename self-contained directories to sc to shorten all the paths

Unresolved Questions

• TBD

Implementation history

• TODO

Some relevant PRs

• https://github.com/rust-lang/rust/pull/96884 (initial design for the component list)
• https://github.com/rust-lang/rust/pull/112910 (initial implementation)
• https://github.com/rust-lang/rust/pull/116014
• https://github.com/rust-lang/rust/pull/116035
• https://github.com/rust-lang/rust/pull/119024
• https://github.com/rust-lang/rust/pull/140525

Start with the stable and unstable documentation for -C link-self-contained, then inspect the rustc_codegen_ssa support mentioned in the checklist and the relevant self-contained target directories. A complete contribution would address one clearly scoped checklist item, with the affected targets behaving consistently and the corresponding documentation updated where needed.