Difference in output of llvm-args=--help-list-hidden when llvm.linked-shared is set to true or false

[csmoe]

I noticed a difference in the output of the llvm-args=--help-list-hidden flag when the llvm.link-shared configuration option is set to true or false in config.toml.

Steps to reproduce on Mac:

1. Set llvm.link-shared=true and llvm.download-ci-llvm=false in the config.toml.
2. ./x.py build
3. ./build/<triple>/stage1/bin/rustc -Cllvm-args=--help-list-hidden | rg emit-dwarf-uwind will print the llvm option

Expected behavior:
The output of llvm-args=--help-list-hidden should be consistent regardless of the value of llvm.link-shared. So The emit-dwarf-unwind option should be present in the output regardless of the llvm.link-shared setting.

Actual behavior:
When llvm.link-shared is set to false, the emit-dwarf-unwind option is missing from the output of llvm-args=--help-list-hidden. And llvm was statically linked within rustc on non-Linux platform, while statically linked on Linux; this difference can be seen on Linux and Mac.

Rust Version: latest nightly

[csmoe]

btw, --emulated-tls is missing regardless of llvm.link-shared.