Turn On WebAssembly Tail Calls

With Safari 18.2 having shipped today, all browsers now support
WebAssembly Tail Calls. This allows the compiler to call a function at
the end of the current function by reusing the stack frame. This should
be a tiny bit faster and allow for recursion without stack overflows...
except that Rust doesn't have any way of guaranteeing this yet, so you
can't really rely on it.

buildCore.js

@@ -6,7 +6,7 @@ let profile = "debug";
 let cargoFlags = "";
 // Keep .github/workflows/ci.yml in sync with these flags, so wasm-opt works.
 let rustFlags =
-    "-C target-feature=+bulk-memory,+mutable-globals,+nontrapping-fptoint,+sign-ext,+simd128,+extended-const,+multivalue,+reference-types";
+    "-C target-feature=+bulk-memory,+mutable-globals,+nontrapping-fptoint,+sign-ext,+simd128,+extended-const,+multivalue,+reference-types,+tail-call";
 let wasmBindgenFlags = "--encode-into always --target web --reference-types";
 let target = "wasm32-unknown-unknown";
 let targetFolder = target;
@@ -28,9 +28,6 @@ if (process.argv.some((v) => v === "--max-opt")) {
 if (process.argv.some((v) => v === "--unstable")) {
     // Relaxed SIMD is not supported by Firefox and Safari yet.
     rustFlags += ",+relaxed-simd";
-
-    // Tail calls are not supported by Safari yet until 18.2 (early December).
-    rustFlags += ",+tail-call";
 }
 
 // Use the nightly toolchain, which enables some more optimizations.