.gitignore: ignore debian/libgtp*

Change-Id: I41fa611917defeab13f01a59dcc3f95961f10bda
diff --git a/.gitignore b/.gitignore
index cb27dff..80e4837 100644
--- a/.gitignore
+++ b/.gitignore
@@ -27,7 +27,7 @@
 # debian
 debian/osmo-ggsn/
 debian/*.debhelper
-debian/libgtp1
+debian/libgtp*/
 debian/osmo-ggsn-dbg
 debian/*.log
 debian/autoreconf.*