修复im-sdk pom文件报错

im-sdk/pom.xml

@@ -43,6 +43,8 @@
 
     </dependencies>
 
+    <build>
+        <plugins>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-source-plugin</artifactId>
@@ -59,5 +61,7 @@
                     </execution>
                 </executions>
             </plugin>
+        </plugins>
+    </build>
 
 </project>