std: Use native `#[thread_local]` TLS on wasm

This commit moves `thread_local!` on WebAssembly targets to using the
`#[thread_local]` attribute in LLVM. This was recently implemented
upstream and is [in the process of being documented][dox]. This change
only takes affect if modules are compiled with `+atomics` which is
currently unstable and a pretty esoteric method of compiling wasm
artifacts.

This "new power" of the wasm toolchain means that the old
`wasm-bindgen-threads` feature of the standard library can be removed
since it should now be possible to create a fully functioning threaded
wasm module without intrusively dealing with libstd symbols or
intrinsics. Yay!

[dox]: https://github.com/WebAssembly/tool-conventions/pull/116

1 files changed, 0 insertions, 0 deletions

diff --git a/src/llvm-project b/src/llvm-project
-Subproject f6446fa8e9629ffb1861303f17930c3aa83ef66
+Subproject 9b64ca5b7e1e3583978f9ac8af6d93b220a13d9