Add EBOOK_LIBS to android build.

Change-Id: I19af7ecf0fe746e6c41c95e647141b4c0af0f6d4
Reviewed-on: https://gerrit.libreoffice.org/6673
Reviewed-by: Tor Lillqvist <tml@collabora.com>
Tested-by: Tor Lillqvist <tml@collabora.com>