Add gpio checkstop handling to Makefile

Add gpio checkstop target to Makefil to build it.

Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/Makefile b/Makefile
index 87acb71..539c7d8 100644
--- a/Makefile
+++ b/Makefile
@@ -3,6 +3,7 @@
 	     boardvpd \
 	     fanctl \
 	     flashbios \
+	     hostcheckstop \
 	     hostwatchdog \
 	     hwmon \
 	     hwmon-barreleye \