Windows does not imply flag bundled-c-zlib

zlib.cabal

@@ -103,7 +103,7 @@ library
   if flag(non-blocking-ffi)
     cpp-options:   -DNON_BLOCKING_FFI
 
-  if flag(bundled-c-zlib) || impl(ghcjs) || os(ghcjs) || os(windows)
+  if flag(bundled-c-zlib) || impl(ghcjs) || os(ghcjs)
     -- We bundle a complete copy of the C sources of zlib-1.3.1,
     -- downloaded via update-c-sources.sh.
     c-sources:   cbits/adler32.c cbits/compress.c cbits/crc32.c
@@ -117,6 +117,7 @@ library
       -- NB: pkg-config is available on windows as well when using msys2
       pkgconfig-depends: zlib
     else
+      -- On Windows zlib is shipped with GHC starting from 7.10
       extra-libraries: z
 
 test-suite tests