compile test_Tensor.cu with CPU

paddle/math/tests/CMakeLists.txt

@@ -14,8 +14,14 @@ add_simple_unittest(test_sparseMatrixCompare)
 add_simple_unittest(test_perturbation)
 add_simple_unittest(test_CpuGpuVector)
 add_simple_unittest(test_Allocator)
-if(COMPILER_SUPPORT_CXX11)
-  LIST(APPEND CUDA_NVCC_FLAGS -std=c++11)
-  CUDA_ADD_EXECUTABLE(test_Tensor test_Tensor.cu)
-  link_paddle_test(test_Tensor)
-endif()
+if(WITH_GPU)
+    if(COMPILER_SUPPORT_CXX11)
+        LIST(APPEND CUDA_NVCC_FLAGS -std=c++11)
+        CUDA_ADD_EXECUTABLE(test_Tensor test_Tensor.cu)
+        link_paddle_test(test_Tensor)
+    endif()
+else()
+    compile_cu_as_cpp(test_Tensor.cu)
+    add_unittest(test_Tensor test_Tensor.cu)
+endif(WITH_GPU)
+