Fix big endian detection

Restrict it to gcc and clang.
msvc should not accidentally enable this code.

Author: AlekseiNikiforovIBM

src/llama-vocab.cpp

@@ -1765,6 +1765,7 @@ void llama_vocab::impl::load(llama_model_loader & ml, const LLM_KV & kv) {
                 const size_t n_precompiled_charsmap = gguf_get_arr_n(ctx, precompiled_charsmap_keyidx);
                 const char * pc = (const char *) gguf_get_arr_data(ctx, precompiled_charsmap_keyidx);
                 precompiled_charsmap.assign(pc, pc + n_precompiled_charsmap);
+#if defined(__GNUC__)
 #if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
                 // correct endiannes of data in precompiled_charsmap binary blob
                 uint32_t * xcda_blob_size = (uint32_t *) &precompiled_charsmap[0];
@@ -1775,6 +1776,7 @@ void llama_vocab::impl::load(llama_model_loader & ml, const LLM_KV & kv) {
                 for (size_t i = 0; i < xcda_array_size; ++i) {
                     xcda_array[i] = __builtin_bswap32(xcda_array[i]);
                 }
+#endif
 #endif
             }
         } else if (tokenizer_model == "rwkv") {