fix(smol): disable LTCG on Windows to prevent LNK2005 linker errors

Removes --with-ltcg flag for Windows builds due to multiply defined
symbol errors between abseil.lib and v8_libbase.lib.

Error: abseil.lib(abseil.mutex.obj) : error LNK2005: absl::Mutex::Dtor
already defined in v8_libbase.lib(v8_libbase.mutex.obj)

Node.js made LTCG optional and disabled by default in PR #21186
specifically to avoid these types of linker conflicts. LTCG remains
enabled for Unix/Linux/macOS builds via --enable-lto.

Trade-off: Slightly larger binary (~5-10MB) but successful builds.

References:
- nodejs/node#21186
- nodejs/node@76ef7ac

Author: jdalton

packages/node-smol-builder/scripts/build.mjs

@@ -1410,9 +1410,10 @@ async function main() {
   if (IS_PROD_BUILD) {
     configureFlags.push('--v8-lite-mode') // -15-20 MB: Disables TurboFan JIT (JS slower, WASM unaffected)
     // Link Time Optimization (very slow, saves ~5-10MB).
-    if (WIN32) {
-      configureFlags.push('--with-ltcg') // Windows: Use MSVC's Link Time Code Generation.
-    } else {
+    // NOTE: LTCG disabled on Windows due to LNK2005 multiply defined symbol errors.
+    // See: https://github.com/nodejs/node/pull/21186 (Node.js made LTCG optional)
+    // Error: abseil.lib(mutex.obj) conflicts with v8_libbase.lib(mutex.obj)
+    if (!WIN32) {
       configureFlags.push('--enable-lto') // Unix/Linux/macOS: Use standard LTO.
     }
   }