watch_queue: add gitignore for generated sample program

Let's keep "git status" happy and quiet.

Fixes: f5b5a164f9a1 ("Add sample notification program")
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/samples/watch_queue/.gitignore b/samples/watch_queue/.gitignore
new file mode 100644
index 0000000..2aa3c7e
--- /dev/null
+++ b/samples/watch_queue/.gitignore
@@ -0,0 +1 @@
+watch_test