Rollup merge of rust-lang#129534 - workingjubilee:ratchet-wasm-c-abi-fcw-to-deny, r=daxpedda,alexcrichton

Deny `wasm_c_abi` lint to nudge the last 25%

This shouldn't affect projects indirectly depending on wasm-bindgen because cargo passes `--cap-lints=allow` when building dependencies.

The motivation is that the ecosystem has mostly taken up the versions of wasm-bindgen that are compatible in general, but ~25% or so of recent downloads remain on lower versions. However, this change might still be unnecessarily disruptive. I mostly propose it as a discussion point.

Author: matthiaskrgr

compiler/rustc_lint_defs/src/builtin.rs

@@ -4771,7 +4771,7 @@ declare_lint! {
     /// version of Rust this will be fixed and therefore dependencies relying
     /// on the non-spec-compliant C ABI will stop functioning.
     pub WASM_C_ABI,
-    Warn,
+    Deny,
     "detects dependencies that are incompatible with the Wasm C ABI",
     @future_incompatible = FutureIncompatibleInfo {
         reason: FutureIncompatibilityReason::FutureReleaseErrorReportInDeps,