message: Add the `posix_filesystem.h` header to the `BUILD` target
diff: @@ -19,6 +19,7 @@ tf_cc_shared_object(
  cc_library(
  name = "posix_filesystem_impl",
  srcs = ["posix_filesystem.cc"],
  + hdrs = ["posix_filesystem.h"],
  deps = [
  ":posix_filesystem_helper",
  "//tensorflow/c:tf_status",
  