Merge branch 'backtrace' into 'main'

mod test {

    use super::*;

    // We test this on Linux only.  This test case is to ensure that we are using the

    // backtrace module correctly, etc., which can be checked by doing it on one platform.

    // Doing it on others simply exposes us to the vagaries of platform backtrace support.

    // Arti ought not to fail its tests just because someone is using a platform with poor

    // backtrace support.

    #[cfg(target_os = "linux")]

    #[test]

    fn internal_macro_test() {

        let start_of_func = line!();