feat: Support for ignored signals with SIGN_IGN

[alokedesai]

📜 Description

💡 Motivation and Context

Currently, if a signal is ignored via SIG_IGN (which is especially common for signals like SIGPIPE), Sentry will still report a fatal, unhandled crash even though the application never received the signal and continued to run just fine.

This PR fixes this behavior by only setting a signal handler to report a crash from signal if the original handler is NOT SIG_IGN

#1472

💚 How did you test it?

Tested locally--by using the local version of Sentry and ensuring sending the SIGPIPE signal (kill -SIGPIPE {pid}) didn't cause a sentry issue to be created. Tested that other signals were not ignored. Would love a way to add tests for this (I assume via an integration test) but from looking at the code it's not clear me to if there's infrastructure to do that currently.

📝 Checklist

• I reviewed the submitted code
• I added tests to verify the changes
• I updated the docs if needed
• Review from the native team if needed
• No breaking changes

🔮 Next steps

[alokedesai]

@philipphofmann would you mind taking a pass on this PR? It's been sitting for a few days. Thanks so much!

[philipphofmann]

Can you please add an entry to the Changelog, please? As I'm not an expert on signal handlers, I need someone from the native team to review this PR.

@Swatinem, can you help us out here, and do you know how to add tests for this? I have no idea how to test signal handlers.

[codecov-commenter]

Codecov Report

Merging #1489 (cbbed26) into master (8564e3a) will not change coverage.
The diff coverage is n/a.

❗ Current head cbbed26 differs from pull request most recent head c88e911. Consider uploading reports for the commit c88e911 to get more accurate results

@@           Coverage Diff           @@
##           master    #1489   +/-   ##
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  Coverage   95.93%   95.93%           
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  Files         157      157           
  Lines        7003     7003           
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  Hits         6718     6718           
  Misses        285      285           

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[alokedesai]

Can you please add an entry to the Changelog, please? As I'm not an expert on signal handlers, I need someone from the native team to review this PR.

@Swatinem, can you help us out here, and do you know how to add tests for this? I have no idea how to test signal handlers.

Sure--added an entry to the changelog. Tried my best to match existing wording but lmk if there are any edits you'd like me to make to it