Currently on Windows when a program panics and the default panic handler is run one of the lines it prints is: note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

The problem is this is not the syntax that powershell (which I think is the default and largest shell used on Windows) uses to set environment variables.

I think note: `RUST_BACKTRACE=1` (or PowerShell `$env:RUST_BACKTRACE=1`) environment variable to display a backtrace would be more correct and better for beginners.

Should be pretty simple change adding a different cfg! branch for following code