cygwin: gzip fpending

pkgs/tools/compression/gzip/default.nix

···
 
   enableParallelBuilding = true;
 
+  preConfigure = if stdenv.isCygwin then ''
+    sed -i lib/fpending.h -e 's,include <stdio_ext.h>,,'
+  '' else null;
+
   # In stdenv-linux, prevent a dependency on bootstrap-tools.
   makeFlags = "SHELL=/bin/sh GREP=grep";