Fix warning in simd indexof on some arm

When pointer compression is disabled, and sizeof(Tagged_t) is 8 (eg,
arm64 without pointer compression), the function
extract_first_nonzero_index is never used, which was causing a warning.


Bug: v8:13048
Change-Id: I5a0fba4da4201e3be147632d891d0d9e20cb46eb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3769694Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Darius Mercadier <dmercadier@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81812}

src/objects/simd.cc

@@ -95,7 +95,7 @@ inline int extract_first_nonzero_index(T v) {
 }
 
 template <>
-inline int extract_first_nonzero_index(uint32x4_t v) {
+V8_ALLOW_UNUSED inline int extract_first_nonzero_index(uint32x4_t v) {
   uint32x4_t mask = {4, 3, 2, 1};
   mask = vandq_u32(mask, v);
   return 4 - vmaxvq_u32(mask);