Integrate gmock to SDK

Change-Id: I4792e4037ffbace4af224cd1bfe0aef63d11a099
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend b/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
index 529002c..9b1a15a 100644
--- a/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
+++ b/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
@@ -1 +1 @@
-RRECOMMENDS_${PN}_append = " gtest sdbusplus phosphor-logging"
+RRECOMMENDS_${PN}_append = " gtest gmock sdbusplus phosphor-logging"