zlib is not exposed to libziparchive headers

By forward-declaring zstream, we don't need to re-export zlib headers.

Bug: 37342627
Test: build
Test: BOARD_VNDK_VERSION=current m -j dumpstate (or any other module
using libziparchive)

Change-Id: Ia69e5d459c79878d491cfe4ca21a7cc8fed4a5d8
1 file changed