Generate UF2 files when no HID available

cmds/cmds.ts

@@ -1,6 +1,8 @@
 /// <reference path="../node_modules/pxt-core/typings/globals/node/index.d.ts"/>
 /// <reference path="../node_modules/pxt-core/built/pxtlib.d.ts" />
 
+import * as fs from 'fs';
+
 require("./editor")
 
 declare namespace pxt.editor {
@@ -9,4 +11,9 @@ declare namespace pxt.editor {
 
 export function deployCoreAsync(resp: pxtc.CompileResult) {
     return pxt.editor.deployCoreAsync(resp, process.env["PXT_SERIAL"] ? false : true)
+        .then(() => {
+            fs.writeFileSync("built/full-" + pxtc.BINARY_UF2, resp.outfiles[pxtc.BINARY_UF2], {
+                encoding: "base64"
+            })
+        })
 }