Add dumpvars for GMS

* For most people and in most enviorments these will
  never pop up, but given we now support GMS variants
  and different build types we ought to tell the user
  which one is in use.

Change-Id: I7639f2e741d9b24e3719ef76d7d532c0155cd988

ui/build/dumpvars.go

@@ -165,7 +165,12 @@ var BannerVars = []string{
 	"BUILD_ID",
 	"OUT_DIR",
 	"SOONG_SDK_SNAPSHOT_TARGET_BUILD_RELEASE",
+	"PRODUCT_IS_ATV",
+	"PRODUCT_IS_AUTOMOTIVE",
 	"WITH_SU",
+	"WITH_GMS",
+	"GMS_MAKEFILE",
+	"MAINLINE_MODULES_MAKEFILE",
 }
 
 func Banner(make_vars map[string]string) string {