error: undefined reference to 'dlsym'

参考：https://stackoverflow.com/a/956698/12338026
bazel中，在linkopts中添加-ldl，如：

cc_binary(
    name = "hdfs_rw",
    srcs = ["hdfs_rw_test.cc"],
    linkopts = [
      "-lpthread",
      "-ldl",
    ],
    ...
)