Add --build-32bit-win switch to configure --help output.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/configure b/configure
index c011436..258c805 100755
--- a/configure
+++ b/configure
@@ -148,6 +148,7 @@
 if test "$show_help" = "yes" ; then
   echo "--cc=                  Specify compiler to use"
   echo "--extra-cflags=        Specify extra CFLAGS to pass to compiler"
+  echo "--build-32bit-win=     Specify yes for a 32-bit build on Windows"
   exit $exit_val
 fi