Add Accelerate/BLAS when using Swift (#765)

Package.swift

@@ -13,7 +13,10 @@ let package = Package(
             path: ".",
             sources: ["ggml.c", "llama.cpp"],
             publicHeadersPath: "spm-headers",
-            cSettings: [.unsafeFlags(["-Wno-shorten-64-to-32"])]
+            cSettings: [.unsafeFlags(["-Wno-shorten-64-to-32"]), .define("GGML_USE_ACCELERATE")],
+            linkerSettings: [
+                .linkedFramework("Accelerate")
+            ]
         ),
     ],
     cxxLanguageStandard: .cxx11