Function helper_write

subprojects/llama.cpp/tests/test-gguf.cpp:155–157

template <typename T>
static void helper_write(FILE * file, const T & val) {
    GGML_ASSERT(fwrite(&val, 1, sizeof(val), file) == sizeof(val));
}

static void helper_write(FILE * file, const void * data, const size_t nbytes) {
    GGML_ASSERT(fwrite(data, 1, nbytes, file) == nbytes);