Use a system includes instead of a local includes for zlib, as the 
Bazel Central Registry version of zlib enforces that only system 
includes are used.

--- a/libs/iostreams/src/zlib.cpp
+++ b/libs/iostreams/src/zlib.cpp
@@ -17,7 +17,7 @@
 #include <boost/throw_exception.hpp>
 #include <boost/iostreams/detail/config/dyn_link.hpp>
 #include <boost/iostreams/filter/zlib.hpp> 
-#include "zlib.h"   // Jean-loup Gailly's and Mark Adler's "zlib.h" header.
+#include <zlib.h>   // Jean-loup Gailly's and Mark Adler's "zlib.h" header.
                     // To configure Boost to work with zlib, see the 
                     // installation instructions here:
                     // http://boost.org/libs/iostreams/doc/index.html?path=7