metal : create autorelease pool during library build (#4970)

* metal : create autorelease pool during library build

ggml-ci

* test : simplify

ggml-ci

tests/test-autorelease.cpp

@@ -0,0 +1,28 @@
+// ref: https://github.com/ggerganov/llama.cpp/issues/4952#issuecomment-1892864763
+
+#include <cstdio>
+#include <string>
+#include <thread>
+
+#include "llama.h"
+
+// This creates a new context inside a pthread and then tries to exit cleanly.
+int main(int argc, char ** argv) {
+    if (argc < 2) {
+        printf("Usage: %s model.gguf\n", argv[0]);
+        return 0; // intentionally return success
+    }
+
+    const std::string fname = argv[1];
+
+    std::thread([&fname]() {
+        llama_backend_init(false);
+        auto * model = llama_load_model_from_file(fname.c_str(), llama_model_default_params());
+        auto * ctx = llama_new_context_with_model(model, llama_context_default_params());
+        llama_free(ctx);
+        llama_free_model(model);
+        llama_backend_free();
+    }).join();
+
+    return 0;
+}