gitignore: add entity-gen.cpp

Add generated file entity-gen.cpp

Change-Id: Id2d13de766b3d4c924bc9a48963e556a9ec86f58
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/.gitignore b/.gitignore
index 92a85ba..5c5f8c1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -62,6 +62,7 @@
 /inventory-sensor-gen.cpp
 /fru-read-gen.cpp
 /channel-gen.cpp
+/entity-gen.cpp
 
 # test related
 /test/sample_unittest