add scala-reflect.jar to the classpath

Fix for the build error:

```
scalac:

BUILD FAILED
/Users/ppicazo/git/aprsdroid/build.xml:120: The following error occurred while executing this line:
jar:file:/Users/ppicazo/git/aprsdroid/tools/scala-compiler.jar!/scala/tools/ant/antlib.xml:5: taskdef A class needed by class scala.tools.ant.FastScalac cannot be found: scala/reflect/internal/settings/MutableSettings$SettingValue
 using the classloader AntClassLoader[/Users/ppicazo/git/aprsdroid/tools/scala-compiler.jar:/Users/ppicazo/git/aprsdroid/tools/scala-library.jar]

Total time: 3 seconds
```