Recompile/rerun test with backtrace

[victoronascimento]

Hi! Thanks a lot for this great mode :) I really think we have top notch IDE experience with it!

One thing I think could make for a killer feature is a binding for recompile/rerun with RUST_BACKTRACE=1.

A common workflow would be:

• navigate to a test and run it (C-c C-c C-c)
• for some reason test fails
• instead of hitting g in the test output buffer to rerun the test after changing something, you want to investigate the stacktrace
• so, we could hit something like s ("enable stacktrace") and then g and it would recompile and rerun the test with RUST_BACKTRACE=1

This would only temporarily enable backtrace for the current run. This is trickier to run with C-u because it is not a "test" argument but more of a compile argument.

Sorry if something like this already exists. I couldn't find it... If this is desirable I could try working on a PR but it might take me a lot of time to get there...

Once again, thanks!