target: Add API for identifying build type

Add API for finding user variant build

Change-Id: Ia91f21ba8a934707bcd640ef234238a6994cb6a0
diff --git a/target/init.c b/target/init.c
index 9c850e5..97809cc 100644
--- a/target/init.c
+++ b/target/init.c
@@ -216,3 +216,13 @@
 {
 	return DDR_CONFIG_VAL;
 }
+
+/* Return Build variant */
+__WEAK bool target_build_variant_user()
+{
+#if USER_BUILD_VARIANT
+	return true;
+#else
+	return false;
+#endif
+}