win: fix test runner build with mingw64

Include `<winioctl.h>` for the definition of `FSCTL_SET_REPARSE_POINT`
and define `ERROR_SYMLINK_NOT_SUPPORTED` if not already defined.

PR-URL: https://github.com/libuv/libuv/pull/1632
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

test/test-fs.c

@@ -32,8 +32,12 @@
     defined(__APPLE__) || defined(_AIX) || defined(__MVS__)
 #include <unistd.h> /* unlink, rmdir, etc. */
 #else
+# include <winioctl.h>
 # include <direct.h>
 # include <io.h>
+# ifndef ERROR_SYMLINK_NOT_SUPPORTED
+#  define ERROR_SYMLINK_NOT_SUPPORTED 1464
+# endif
 # define unlink _unlink
 # define rmdir _rmdir
 # define open _open