swift : add missing c file to Package.swift (#2978)

Package.swift

@@ -12,7 +12,7 @@ let package = Package(
             name: "llama",
             path: ".",
             exclude: ["ggml-metal.metal"],
-            sources: ["ggml.c", "llama.cpp"],
+            sources: ["ggml.c", "llama.cpp", "ggml-alloc.c"],
             publicHeadersPath: "spm-headers",
             cSettings: [.unsafeFlags(["-Wno-shorten-64-to-32"]), .define("GGML_USE_ACCELERATE")],
             linkerSettings: [