Handle EINTR correctly in forkserver

[arata-nvm]

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Related Issue

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• Importance of the issue
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  • Small (trivial changes, such as build error)

PR Overview

fuzzuf-cc has an issue with forkserver terminating with the following error:

[!] [FdChannel] Failed to send: ExecutePUT (Requested 4 bytes, Sent -1 bytes): Broken pipe

This is because read function can return EINTR, which is not being handled correctly.
This PR fixes this issue by modifying Recv function in forkserver to handle EINTR.

Concerns (Optional)

• Performance
• Source Code Quality

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[retrage]

It looks good to me