Avoid creating executable files

[ramikg]

Description

This PR removes all executable bits in calls to os.OpenFile() or os.WriteFile().

Previously, the file mode passed to these functions was os.ModePerm (which is equal to 0777, i.e. read/write/execute for everyone), which may have undesirable consequences.
This value is sometimes used by Go programmers because it is conveniently exported in the os package, but it's intended usage is as a bitmask, and not as a file mode.
I've changed this value to 0666 (i.e. removed the executable bits), like the one used by Go's os.Create().

Checklist

• Code compiles correctly
• Run make fmt to fix inconsistent formats
• Run make lint to get lint errors and fix all of them
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[ramikg]

I have read the CLA Document and I hereby sign the CLA

[sfc-gh-pfus]

Hello @ramikg ! We are really thankful for your initiative! If you would like to implement boy scout rule and address some of my comments it would be really great. Thanks!

[ramikg]

Hello @ramikg ! We are really thankful for your initiative! If you would like to implement boy scout rule and address some of my comments it would be really great. Thanks!

Thank you. I've addressed all comments except for one, which I've commented on.

[sfc-gh-pfus]

Thanks a lot! I answered your concern, I hope that I can convince you.

[sfc-gh-pfus]

@ramikg thank you very much for you input! Your help is appreciated :) Unfortunately, our policy does not allow direct merges from community, but I marked you as co-authored-by in the git commit.