extras/tools: check for ant when bootstrapping

This was accidentally left out of b3050f68.
Signed-off-by: Tristan Matthews <tmatth@videolan.org>

extras/tools/bootstrap

@@ -81,6 +81,7 @@ check_tar
 check ragel
 check_sed
 check protoc
+check ant
 
 [ -n "$NEEDED" ] && mkdir -p build/