Improve panic reporting

[flowchartsman]

From a UX perspective, "Error: runtime error: invalid memory address or nil pointer dereference" is not particularly helpful if I've made a mistake in my magefile that causes a panic, since there's zero context to localize it. Though I appreciate the desire to keep error message parsimonious in a build tool, it would be super helpful if I could get a full stacktrace when running with -debug or at least the relevant location of the panic without -debug

[natefinch]

yeah 100%. I think this is just not a flow I have spent a lot of time on. Just dumping the regular panic message shouldn't be too hard.