Fix output file path when package is not set

It's been "out//Foo.java" when the package is not set.
Now, it's fixed to return "out/Foo.java".

Bug: none
Test: aidl_unittests/ aidl_integration_test
Change-Id: Id175e369d591932fe1ce87f1c7e641d8dfa3cfa4
2 files changed