Currently, when enabling CFI via -Zsanitizer=cfi and executing e.g.
std::sys::random::getrandom, we can observe a CFI violation. This is
the case for all consumers of the std::sys::pal::weak::weak macro,
as it is defining weak functions which don't show up in LLVM IR
metadata. CFI fails for all these functions.
Similar to other such cases in
https://github.com/rust-lang/rust/issues/115199, this change stops
emitting the CFI typecheck for consumers of the macro via the
\#[no_sanitize(cfi)] attribute.
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