Add OS X specific delay after waiting for upload port, to prevent "Resource busy" errors on open

arduino-core/src/cc/arduino/packages/uploaders/SerialUploader.java

@@ -136,6 +136,12 @@ public class SerialUploader extends Uploader {
           // it happened within 250 ms. So we wait until the reset should
           // have already occured before we start scanning.
           actualUploadPort = waitForUploadPort(userSelectedUploadPort, before);
+          
+          if (OSUtils.isMacOS()) {
+        	  // on OS X, if the port is opened too quickly after it is detected,
+        	  // a "Resource busy" error occurs, add a delay to workaround this
+        	  Thread.sleep(250);
+          }
         }
       } catch (SerialException e) {
         throw new RunnerException(e);