Fix zlib

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

cmake/FindZLIB.cmake

@@ -1,5 +1,9 @@
 if(NOT ZLIB_FOUND)
-  set(Z_HAVE_UNISTD_H ON)
+  if(UNIX OR CMAKE_SYSTEM_NAME STREQUAL "MSYS")
+    set(Z_HAVE_UNISTD_H ON)
+  else()
+    set(Z_HAVE_UNISTD_H OFF)
+  endif()
   configure_file("${PROJECT_SOURCE_DIR}/vendor/zlib/zconf.h.cmakein"
     "${CMAKE_CURRENT_BINARY_DIR}/zlib/zconf.h" @ONLY)