gtest: Ensure added to SDK

Change-Id: I51e1ea4bcedbb64ed6e628e9a61dca6da35affb5
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend b/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
new file mode 100644
index 0000000..2bbb39a
--- /dev/null
+++ b/common/recipes-core/packagegroups/packagegroup-core-standalone-sdk-target.bbappend
@@ -0,0 +1 @@
+RRECOMMENDS_${PN}_append = " gtest"