tools/: add __pycache__ to gitignore

Change-Id: Iaddfe140df1e82611df8e2594b7560e3bdafd896
diff --git a/tools/.gitignore b/tools/.gitignore
new file mode 100644
index 0000000..bee8a64
--- /dev/null
+++ b/tools/.gitignore
@@ -0,0 +1 @@
+__pycache__