Fix mcl build under ninja

CMakeLists.txt

@@ -246,12 +246,12 @@ elseif(TARGET_PROCESSOR STREQUAL "x86_64" AND NOT APPLE)
 	add_custom_command(OUTPUT ${MSM_OBJ}
 		COMMAND ${CMAKE_CXX_COMPILER} -c -o ${MSM_OBJ} ${CMAKE_CURRENT_SOURCE_DIR}/src/msm_avx.cpp ${MCL_COMPILE_OPTIONS} -I ${CMAKE_CURRENT_SOURCE_DIR}/include -mavx512f -mavx512ifma -std=c++11 -fno-exceptions -fno-rtti -DCYBOZU_DONT_USE_STRING -DCYBOZU_DONT_USE_EXCEPTION -DNDEBUG
 		WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})
-	add_custom_target(msm_avx.o
+	add_custom_target(msm_avx
 		SOURCES ${MSM_OBJ})
 	target_link_libraries(mcl PUBLIC ${MSM_OBJ})
-	add_dependencies(mcl msm_avx.o)
+	add_dependencies(mcl msm_avx)
 	target_link_libraries(mcl_st PUBLIC ${MSM_OBJ})
-	add_dependencies(mcl_st msm_avx.o)
+	add_dependencies(mcl_st msm_avx)
 	target_sources(mcl_st PRIVATE ${MSM_OBJ})
 endif()