gitignore: add *.netcat.stderr

Change-Id: I0119153aa0a7f035f067c5a8607f8f1930b9fc1c
diff --git a/.gitignore b/.gitignore
index 519dc48..41add91 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,3 +16,4 @@
 !bin/Makefile
 !deps/Makefile
 .*.sw?
+*.netcat.stderr