Fix output name of embedded library,

honor OUTPUT_NAME in MERGE_LIBRARIES macro

cmake/libutils.cmake

@@ -220,7 +220,7 @@ MACRO(MERGE_LIBRARIES)
   SET(LIBS ${ARG_DEFAULT_ARGS})
   LIST(REMOVE_AT LIBS 0)
   IF(ARG_STATIC)
-    IF (NOT "${ARG_OUTPUT_NAME}")
+    IF (NOT ARG_OUTPUT_NAME)
       SET(ARG_OUTPUT_NAME ${TARGET})
     ENDIF()
     MERGE_STATIC_LIBS(${TARGET} ${ARG_OUTPUT_NAME} "${LIBS}")