[wasm-simd] Fix endianness issue when generating constants

value must be written to memory in LE order on BE machines
as they will be loaded in reverse when emitting S128Const.

Change-Id: Ia1d6c784505abe499fb71a6d86daea2721615da4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3151956Reviewed-by: Zhi An Ng <zhin@chromium.org>
Commit-Queue: Milad Fa <mfarazma@redhat.com>
Cr-Commit-Position: refs/heads/main@{#76758}

test/cctest/wasm/test-run-wasm-simd.cc

@@ -367,7 +367,8 @@ void RunF128CompareOpConstImmTest(
     byte temp = r.AllocateLocal(kWasmS128);
     uint8_t const_buffer[kSimd128Size];
     for (size_t i = 0; i < kSimd128Size / sizeof(FloatType); i++) {
-      memcpy(&const_buffer[i * sizeof(FloatType)], &x, sizeof(FloatType));
+      WriteLittleEndianValue<FloatType>(
+          bit_cast<FloatType*>(&const_buffer[0]) + i, x);
     }
     BUILD(r,
           WASM_LOCAL_SET(temp,