[llvm] [Instrumentation][nsan] Intrinsic tests + bugfixes (PR #186803)

[Lewis Crawford via llvm-commits]

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LewisCrawford wrote:

Ah, I wasn't sure whether that FIXME was still relevant since the current version is using f80 instead of double. I'll add an updated comment to the new test file.

https://github.com/llvm/llvm-project/pull/186803