Patch grpc for Windows

[mehrdadn]

Why are these changes needed?

Need quoting to avoid splitting on spaces in file path.

Related issue number

#631

grpc/grpc#20820

Checks

• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://ray.readthedocs.io/en/latest/.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failure rates at https://ray-travis-tracker.herokuapp.com/.

[AmplabJenkins]

Can one of the admins verify this patch?

[simon-mo]

Should we consider using appveyor or azure pipeline to add windows into our CI? (cc @pcmoritz)

[mehrdadn]

Yes, but I'm not familiar with either, so I don't know what the trade-offs are. If you guys have details I might able to help with making a choice.

[robertnishihara]

@simon-mo @mehrdadn, last time I discussed this with @pcmoritz, GitHub actions seemed like a good option to explore (or potentially Azure pipelines).

[AmplabJenkins]

Test PASSed.
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https://amplab.cs.berkeley.edu/jenkins//job/Ray-PRB/18916/
Test PASSed.