fix: windows build issue

[ioanatflowcrypt]

This PR fixed build issue in windows system

close #5610 // if this PR closes an issue

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Tests (delete all except exactly one):

• Does not need tests (refactor only, docs or internal changes)

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• addresses the issue it closes (if any)
• code is readable and understandable
• is accompanied with tests, or tests are not needed
• is free of vulnerabilities
• is documented clearly and usefully, or doesn't need documentation

[ioanatflowcrypt]

@sosnovsky Maybe better to include below tutorial to install rsync in git bash in our readme?

In windows git bash, rsync is not installed by default and we use rsync in build.sh.

Here's tutorial to install rsync in git bash.

https://www.chrisborkowski.com/git-bash-here-and-rsync-it/

[sosnovsky]

@ioanmo226 looks like CI checks are not performed for non-FlowCrypt contributors, probably it'll be easier if you'll just create another PR with your usual account