Auto merge of #64438 - cuviper:beta-rollup, r=Mark-Simulacrum

[beta] Rollup backports

Cherry-picked:

- Permit unwinding through FFI by default #62603
- pprust: Do not print spaces before some tokens #63897
- Account for doc comments coming from proc macros without spans #63930
- Support "soft" feature-gating using a lint #64066
- Update xLTO compatibility table in rustc book. #64092
- Include compiler-rt in the source tarball #64240
- Update LLVM submodule #64317

r? @Mark-Simulacrum