Auto merge of #370 - larsbergstrom:retry_windows_caching, r=aneeshusa
Auto merge of #370 - larsbergstrom:retry_windows_caching, r=aneeshusa

Enable caching deps on Windows, this time with UNIX paths

r? @aneeshusa @edunham

*this* time, I tested it locally on the build machine itself inside of a MINGW64 shell that I believe reproduces the exact environment, and it seemed to work.

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rwaweber/saltfs,servo/saltfs,UK992/saltfs,ALikhachev/saltfs,rwaweber/saltfs,servo/saltfs,UK992/saltfs,ALikhachev/saltfs,UK992/saltfs,ALikhachev/saltfs,rwaweber/saltfs