why .so library become very big after compile with cmake?

I recently encountered a project need to use cmake compiled .so library.When compiled with ndk-build, the size of .so library is 415k.When compiled with cmake , the size of .so library is 4.5M.

plugin for Gradle versio:gradle:3.0.0', gradle version: gradle-4.1-all.zip

build.gradle cmake configuration：

ndk {
        abiFilters 'armeabi','armeabi-v7a','x86'
    }

    externalNativeBuild {
        cmake {
            arguments '-DANDROID_PLATFORM=android-21',
                    '-DANDROID_TOOLCHAIN=clang',
                    '-DCMAKE_BUILD_TYPE=Release'
            targets 'device'
        }
    }

CMakeLists.txt file is as follows:

cmake_minimum_required(VERSION 3.4.1)
set (CMAKE_CXX_STANDARD 14)

set(CMAKE_VERBOSE_MAKEFILE ON)

add_library(so SHARED  IMPORTED)

set_target_properties( 
                  so 
                  PROPERTIES IMPORTED_LOCATION
                  ${CMAKE_SOURCE_DIR}/../jniLibs/${ANDROID_ABI}/so.so)


add_library( 
         myso
         SHARED
         XXX.cpp
         .......
         xxx.c
         ...
         )

target_include_directories(myso  PRIVATE
                       src
                       .....
                       )

find_library( 
          log-lib
          log )
target_link_libraries( 
                   myso
                   so 
                   android
                   log
                   )
set(distribution_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../../dis)
set_target_properties(myso  
                  PROPERTIES
                  LIBRARY_OUTPUT_DIRECTORY
                  "${distribution_DIR}/lib/${ANDROID_ABI}")

I compare the symbols in two .so library files and found that the small .so library has 1000 lines, The same as the first 1000 lines of the big .so library, the larger ones have more symbols than the smaller ones. Is my cmake configuration wrong?