test: Make sure mocks compile

This makes sure we don't accidentally change our interface without
updating the mock.

Change-Id: I50c6827e637167f1223d91f724b99ef8a24b107f
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/.gitignore b/.gitignore
index 9154cb2..15f8350 100644
--- a/.gitignore
+++ b/.gitignore
@@ -46,4 +46,5 @@
 /test/event
 /test/handle
 /test/internal/fd
+/test/mocks
 /test/utility/aspeed