rustc_codegen_llvm: Simplify wide-arithmetic conversion

This commit simplifies conversion of the target feature `wide-arithmetic`
on WebAssembly architectures as only the major version is relevant.

It also slightly changes the corresponding comment.

Author: a4lg

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -287,9 +287,9 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
             s,
             smallvec![TargetFeatureFoldStrength::EnableOnly("evex512")],
         )),
-        // Support for `wide-arithmetic` will first land in LLVM 20 as part of
+        // Support for `wide-arithmetic` landed in LLVM 20 as part of
         // llvm/llvm-project#111598
-        ("wasm32" | "wasm64", "wide-arithmetic") if get_version() < (20, 0, 0) => None,
+        ("wasm32" | "wasm64", "wide-arithmetic") if major < 20 => None,
         ("sparc", "leoncasa") => Some(LLVMFeature::new("hasleoncasa")),
         // In LLVM 19, there is no `v8plus` feature and `v9` means "SPARC-V9 instruction available and SPARC-V8+ ABI used".
         // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.0/llvm/lib/Target/Sparc/MCTargetDesc/SparcELFObjectWriter.cpp#L27-L28