Remove read-only flags when installing on Windows

[danielkcz]

Do you want to request a feature or report a bug?
Both (kinda)

What is the current behavior?
Installing package on Windows that was published with read-only flags, keeps those flags and this prevents and further use of Yarn.

If the current behavior is a bug, please provide the steps to reproduce.
yarn add firebase
yarn add debug
(on Windows)

What is the expected behavior?
Apparently NPM is removing read-only flags when installing package. Yarn should follow similar footsteps.

Additional information
This is coming from the #992 and I wanted to summarize the actual issue here and what needs to be done. I think that issue should be closed now.

Windows 10 x64, Yarn 0.17.7, Node 6.9.1

[Daniel15]

I don't think this is specific to Windows (I feel like #872 is the same issue)

[danielkcz]

I see, might be true. Either way it apparently needs to be solved on Yarn side by fixing those permissions instead of trusting that they are correctly set within the package.

[danielkcz]

Nevermind here, apparently this is a duplicate of #961