Replace ScopedFd with unique_fd

aidl-cpp will generate code using unique_fd in the near future.

While here, also make the binder intermediates library depend on
libbinder in order to obtain proper header include paths.

Bug: 27804373
Test: Compiles with accompanying changes.

Change-Id: I6098e63f179ac81096fa4775cc11e59e87a962c9