Temporarily add back -Zwasm-c-abi=spec

compiler/rustc_session/src/config.rs

@@ -3118,6 +3118,7 @@ pub(crate) mod dep_tracking {
     }
 
     impl_dep_tracking_hash_via_hash!(
+        (),
         AutoDiff,
         bool,
         usize,

compiler/rustc_session/src/options.rs

@@ -802,6 +802,7 @@ mod desc {
         "either a boolean (`yes`, `no`, `on`, `off`, etc), or a non-negative number";
     pub(crate) const parse_llvm_module_flag: &str = "<key>:<type>:<value>:<behavior>. Type must currently be `u32`. Behavior should be one of (`error`, `warning`, `require`, `override`, `append`, `appendunique`, `max`, `min`)";
     pub(crate) const parse_function_return: &str = "`keep` or `thunk-extern`";
+    pub(crate) const parse_wasm_c_abi: &str = "`spec`";
     pub(crate) const parse_mir_include_spans: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), or `nll` (default: `nll`)";
     pub(crate) const parse_align: &str = "a number that is a power of 2 between 1 and 2^29";
@@ -1897,6 +1898,10 @@ pub mod parse {
         true
     }
 
+    pub(crate) fn parse_wasm_c_abi(_slot: &mut (), v: Option<&str>) -> bool {
+        v == Some("spec")
+    }
+
     pub(crate) fn parse_mir_include_spans(slot: &mut MirIncludeSpans, v: Option<&str>) -> bool {
         *slot = match v {
             Some("on" | "yes" | "y" | "true") | None => MirIncludeSpans::On,
@@ -2631,6 +2636,11 @@ written to standard error output)"),
         Requires `-Clto[=[fat,yes]]`"),
     wasi_exec_model: Option<WasiExecModel> = (None, parse_wasi_exec_model, [TRACKED],
         "whether to build a wasi command or reactor"),
+    // This option only still exists to provide a more gradual transition path for people who need
+    // the spec-complaint C ABI to be used.
+    // FIXME remove this after a couple releases
+    wasm_c_abi: () = ((), parse_wasm_c_abi, [TRACKED],
+        "use spec-compliant C ABI for `wasm32-unknown-unknown` (deprecated, always enabled)"),
     write_long_types_to_disk: bool = (true, parse_bool, [UNTRACKED],
         "whether long type names should be written to files instead of being printed in errors"),
     // tidy-alphabetical-end