proc_macro does not have a constructor for c string literals

[MaxVerevkin]

C string literals have been stabilized (#117472) but there is no way to create them in proc macros.

[Noratrieb]

That's not good, I'm sure a PR adding it would be welcome. cc @rust-lang/libs-api

[novafacing]

This should be resolved by #119750 / #119651. C String literals can now be constructed like:

let lit = proc_macro::Literal::c_string(c"a");

(or, equivalently)

let lit = proc_macro::Literal::c_string(&std::ffi::CString::new("a").unwrap());

[fmease]

Closing as superseded by the libs-api tracking issue.