Update setup.py to allow pip install . (#959)

* Update setup.py

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Change BUILD to BUILD.bazel to avoid name collision on Windows

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Fix permission issue

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Updates README.md

Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

.kokorun/io_cpu.sh

@@ -56,6 +56,8 @@ docker run -i --rm -v $PWD:/v -w /v --net=host \
   -e BAZEL_OPTIMIZATION="${BAZEL_OPTIMIZATION}" \
   gcr.io/tensorflow-testing/nosla-ubuntu16.04-manylinux2010@sha256:3a9b4820021801b1fa7d0592c1738483ac7abc209fc6ee8c9ef06cf2eab2d170 /v/.github/workflows/build.bazel.sh
 
+sudo chown -R $(id -nu):$(id -ng) .
+
 docker run -i --rm --user $(id -u):$(id -g) -v /etc/password:/etc/password -v $PWD:/v -w /v --net=host \
   python:${PYTHON_VERSION}-slim python setup.py --data build -q bdist_wheel
 

README.md

@@ -288,6 +288,34 @@ TFIO_DATAPATH=bazel-bin \
     'python3 -m pytest -s -v tests/test_serialization_eager.py'
 ```
 
+#### Python Wheels
+
+It is possible to build python wheels after bazel build is complete with the following command:
+```
+python3 setup.py bdist_wheel --data bazel-bin
+```
+The whl file is will be available in dist directory. Note the bazel binary directory `bazel-bin`
+has to be passed with `--data` args in order for setup.py to locate the necessary share objects,
+as `bazel-bin` is outside of the `tensorflow_io` package directory.
+
+Alternatively, source install could be done with:
+```
+TFIO_DATAPATH=bazel-bin python3 -m pip install .
+```
+with `TFIO_DATAPATH=bazel-bin` passed for the same readon.
+
+Note installing with `-e` is different from the above. The 
+```
+TFIO_DATAPATH=bazel-bin python3 -m pip install -e .
+```
+will not install shared object automatically even with `TFIO_DATAPATH=bazel-bin`. Instead,
+`TFIO_DATAPATH=bazel-bin` has to be passed everytime the program is run after the install:
+```
+TFIO_DATAPATH=bazel-bin python3
+# import tensorflow_io as tfio
+# ...
+```
+
 #### Docker
 
 For Python development, a reference Dockerfile [here](tools/dev/Dockerfile) can be