Makefile changes for generating inventory-sensor-gen.cpp

Provide capability for the recipe to pass the config yaml as a
configurable output. Fallback to inventory-sensor-example.yaml
in case no config yaml is passed.

Change-Id: I6a069b0925c3e4c4d56bd1c9767b8fadcdf433b4
Signed-off-by: Tom Joseph <tomjoseph@in.ibm.com>
diff --git a/.gitignore b/.gitignore
index 4a34745..c468989 100644
--- a/.gitignore
+++ b/.gitignore
@@ -55,3 +55,4 @@
 /test/*.trs
 /ipmiwhitelist.cpp
 /sensor-gen.cpp
+/inventory-sensor-gen.cpp