[ci][SWIG] fixed SWIG -Wstrict-aliasing warnings (#2139)

CMakeLists.txt

@@ -117,6 +117,9 @@ endif(USE_HDFS)
 
 if(UNIX OR MINGW OR CYGWIN)
     SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -pthread -O3 -Wextra -Wall -Wno-ignored-attributes -Wno-unknown-pragmas -Wno-return-type")
+    if(USE_SWIG)
+        SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-strict-aliasing")
+    endif()
 endif()
 
 if(WIN32 AND MINGW)