fix python full coverage decrease issue (#31429)

* fix python full coverage decrease issue

* fix

cmake/generic.cmake

@@ -797,7 +797,8 @@ function(py_test TARGET_NAME)
     if(WITH_COVERAGE AND NOT (WITH_INCREMENTAL_COVERAGE AND "$ENV{PADDLE_GIT_DIFF_PY_FILE}" STREQUAL ""))
       add_test(NAME ${TARGET_NAME}
               COMMAND ${CMAKE_COMMAND} -E env FLAGS_init_allocated_mem=true FLAGS_cudnn_deterministic=true
-              FLAGS_cpu_deterministic=true ${py_test_ENVS}
+              FLAGS_cpu_deterministic=true
+              PYTHONPATH=${PADDLE_BINARY_DIR}/python ${py_test_ENVS}
               COVERAGE_FILE=${PADDLE_BINARY_DIR}/python-coverage.data
               ${PYTHON_EXECUTABLE} -m coverage run --branch -p ${py_test_SRCS} ${py_test_ARGS}
               WORKING_DIRECTORY ${CMAKE_CURRENT_BINARY_DIR})