Add changes for configuring macos support in spm (#12)

* add changes for configuring macos support in spm

* test latest version downloading artifacts

* update back to using latest from main

* update using latestfrombranch

---------

Co-authored-by: rachguo <rachguo@rachguos-Mini.attlocal.net>
Co-authored-by: rachguo <rachguo@rachguos-Mac-mini.local>

Package.swift

@@ -20,7 +20,8 @@ import class Foundation.ProcessInfo
 
 let package = Package(
     name: "onnxruntime",
-    platforms: [.iOS(.v12)],
+    platforms: [.iOS(.v12),
+                .macOS(.v11)],
     products: [
         .library(name: "onnxruntime",
                  type: .static,