./configure: A better way to exclude fetching //tensorflow/examples/android/.. (#6829)

After
https://github.com/bazelbuild/bazel/commit/0b9ebfee8d7f3bd5cf68f4dba4790bf3fed9349d
//tensorflow/examples/android/... has to be excluded during bazel fetch.

Using the workaround mentioned in
https://github.com/bazelbuild/bazel/issues/2220, so that it works on
both Linux and Windows.