Build: Set object extension to .o in NS toolchain

Change-Id: Ia19b8272d6bab59f038f78ebe5d91f93e46af24b
Signed-off-by: David Hu <david.hu@arm.com>
diff --git a/cmake/install.cmake b/cmake/install.cmake
index cd3d808..a25a64d 100644
--- a/cmake/install.cmake
+++ b/cmake/install.cmake
@@ -159,7 +159,6 @@
             DESTINATION ${INSTALL_INTERFACE_SRC_DIR})
 endif()
 
-
 ##################### Export image signing information #########################
 
 if(BL2)
@@ -260,3 +259,7 @@
 
 configure_file(${CMAKE_SOURCE_DIR}/config/spe_config.cmake.in
                ${INSTALL_CMAKE_DIR}/spe_config.cmake @ONLY)
+
+# Toolchain utils
+install(FILES       cmake/set_extensions.cmake
+        DESTINATION ${INSTALL_CMAKE_DIR})