message: examples.gnu_builder: Use zlib_version to determine the library name on macOS.
diff: @@ -131,7 +131,7 @@ def configure(cxx_toolkit = None,
  zlib_configure_call = zlib_configure
  zlib_makefile = None
  if cxx_toolkit.os is drake.os.macos:
  - zlib_lib = drake.cxx.DynLib('zlib/lib/libz.1.2.8.dylib')
  + zlib_lib = drake.cxx.DynLib('zlib/lib/libz.%s.dylib' % zlib_version)
  elif cxx_toolkit.os is drake.os.linux:
  zlib_lib = drake.cxx.DynLib('zlib/lib/libz.so.1')
  zlib_prefix_absolute = drake.path_build(zlib_prefix, absolute = True)
  