Add support for intel_s1000 SoC which is based on Xtensa arch

Signed-off-by: Rajavardhan Gundi <rajavardhan.gundi@intel.com>
diff --git a/boot/zephyr/CMakeLists.txt b/boot/zephyr/CMakeLists.txt
index 15c2ece..b5c754e 100644
--- a/boot/zephyr/CMakeLists.txt
+++ b/boot/zephyr/CMakeLists.txt
@@ -36,6 +36,11 @@
   set(DTC_OVERLAY_FILE ${CMAKE_CURRENT_LIST_DIR}/dts.overlay)
 endif()
 
+if (EXISTS ${CMAKE_CURRENT_LIST_DIR}/boards/${BOARD}.overlay)
+  set(DTC_OVERLAY_FILE
+      "${DTC_OVERLAY_FILE} ${CMAKE_CURRENT_LIST_DIR}/boards/${BOARD}.overlay")
+endif()
+
 # Enable Zephyr runner options which request mass erase if so
 # configured.
 #