merge libomp.a into libpaddle-mobile.a for ios device

CMakeLists.txt

@@ -150,7 +150,17 @@ if (ANDROID_NDK_TOOLCHAIN_INCLUDED)
     list(REMOVE_DUPLICATES CMAKE_CXX_FLAGS)
     add_library(paddle-mobile SHARED ${PADDLE_MOBILE_CC} ${PADDLE_MOBILE_H})
 elseif(IS_IOS)
+    if(USE_OPENMP)
+        add_library(paddle-mobile-stage0 STATIC ${PADDLE_MOBILE_CC} ${PADDLE_MOBILE_H})
+        add_custom_target(paddle-mobile ALL
+            COMMAND libtool -static -o ${CMAKE_BINARY_DIR}/libpaddle-mobile.a ${CMAKE_CURRENT_LIST_DIR}/tools/libomp.a $<TARGET_FILE:paddle-mobile-stage0>
+            WORKING_DIRECTORY ${CMAKE_BINARY_DIR}
+            DEPENDS paddle-mobile
+        )
+        add_dependencies(paddle-mobile paddle-mobile-stage0)
+    else()
         add_library(paddle-mobile STATIC ${PADDLE_MOBILE_CC} ${PADDLE_MOBILE_H})
+    endif()
 else ()
     add_library(paddle-mobile SHARED ${PADDLE_MOBILE_CC} ${PADDLE_MOBILE_H})
 endif ()