Do not crash when looking for Java
Do not crash when looking for Java

Summary: `os.listdir(base_path)` fails if `base_path` does not exist.

Reviewed By: irenewchen

shipit-source-id: 6861aabc3aa5deb00e385656aaa55423c0266846

facebook/buck,Addepar/buck,nguyentruongtho/buck,JoelMarcey/buck,kageiit/buck,Addepar/buck,JoelMarcey/buck,facebook/buck,nguyentruongtho/buck,kageiit/buck,JoelMarcey/buck,nguyentruongtho/buck,nguyentruongtho/buck,JoelMarcey/buck,JoelMarcey/buck,Addepar/buck,Addepar/buck,facebook/buck,Addepar/buck,Addepar/buck,JoelMarcey/buck,kageiit/buck,facebook/buck,kageiit/buck,JoelMarcey/buck,JoelMarcey/buck,nguyentruongtho/buck,Addepar/buck,nguyentruongtho/buck,facebook/buck,facebook/buck,JoelMarcey/buck,Addepar/buck,kageiit/buck,Addepar/buck,JoelMarcey/buck,JoelMarcey/buck,nguyentruongtho/buck,kageiit/buck,Addepar/buck,kageiit/buck,facebook/buck,Addepar/buck,Addepar/buck,JoelMarcey/buck,JoelMarcey/buck,Addepar/buck